This PDF file contains the front matter associated with SPIE Proceedings Volume 9671, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Many kinds of optimization algorithm have been applied to design diffractive optical elements (DOEs) for beam shaping. However, only the selected sampling points are controlled by these optimization algorithms, the intensity distribution of other points on the output plane is always far away from the ideal distribution. In our previous research, the non-selected points were well controlled by using a hybrid algorithm merging hill-climbing with simulated annealing, but this hybrid algorithm is time-consuming. In this paper, a new hybrid algorithm merging Gerchberg-Saxton algorithm with gradient method is presented. Because of the use of iterative algorithm, the optimization time is largely reduced. The intensity distribution of the non-selected points as well as that of the selected points is well controlled, and good performance of beam shaping is obtained. Finally the experimental results demonstrate the good performance of this algorithm.

Object to the high precision flying target attitude measurement issues of a large space and large field of view, comparing existing measurement methods, the idea is proposed of using two array CCD to assist in identifying the three linear CCD with multi-cooperative target attitude measurement system, and to address the existing nonlinear system errors and calibration parameters and more problems with nine linear CCD spectroscopic test system of too complicated constraints among camera position caused by excessive. The mathematical model of binocular vision and three linear CCD test system are established, co-spot composition triangle utilize three red LED position light, three points’ coordinates are given in advance by Cooperate Measuring Machine, the red LED in the composition of the three sides of a triangle adds three blue LED light points as an auxiliary, so that array CCD is easier to identify three red LED light points, and linear CCD camera is installed of a red filter to filter out the blue LED light points while reducing stray light. Using array CCD to measure the spot, identifying and calculating the spatial coordinates solutions of red LED light points, while utilizing linear CCD to measure three red LED spot for solving linear CCD test system, which can be drawn from 27 solution. Measured with array CCD coordinates auxiliary linear CCD has achieved spot identification, and has solved the difficult problems of multi-objective linear CCD identification. Unique combination of linear CCD imaging features, linear CCD special cylindrical lens system is developed using telecentric optical design, the energy center of the spot position in the depth range of convergence in the direction is perpendicular to the optical axis of the small changes ensuring highprecision image quality, and the entire test system improves spatial object attitude measurement speed and precision.

In order to obtain frequency-locked laser beam with widely tunable frequency- offset used in a clod atom interferometer, a frequency stabilization method using a fiber electro-optic modulator (FEOM) is proposed. In this method, the laser passing through a FEOM can be locked with a wide-range frequency-offset, avoiding the frequency and power jitter caused by internal modulation on the current or PZT at the same time. To evaluate the outcome of this method, a beat signal between the frequency-shifted laser and the laser locked by Doppler-free Dichroic Atomic Vapor Laser Lock was measured. The analysis of the experimental results shows that the frequency-offset of the laser beam, with a full width at half maximum less than 1 MHz, can be tuned from 200 MHz to 10 GHz, which successfully meets the requirements of cold atom interferometer.

In large-scale three-dimensional (3D) coordinates measurement, to solve the problem of structured light sensor’s measurement data from different measurement stations unifying to the global coordinate system, a method based on workshop Measuring Position System (wMPS) global controlling is researched to concentrate the structured light sensor’s measurement data to the global coordinate system automatically. According to the measurement principle, two calibration methods are proposed to calibrate the structural parameters based on a standard ball, one is transferring stations based on common points and the other is fitting ball equation. Finally, a platform for experiment is built to verify the two calibration methods. Experimental results show that the average measurement error on 10 points is 0.127 mm according to the laser tracker of the first method and the other average error is 0.101 mm, both the two calibration methods have a high precision to meet the demands of large-scale 3D coordinates measurement.

A stable high-repetition-rate, high pulse energy and single-frequency electro-optic Q-switched laser has been developed and demonstrated in this paper. The prelase technique has been used in this single-frequency laser. And a PID feedback control electronics is applied to stabilize the prelase. Meanwhile, a two-plate resonant reflector take the place of traditional dielectric output coupler mirror to enhance the single-axial-mode selection. And a Cr:YAG saturable absorber is also inserted in the cavity to improve single-axial-mode selection. Output laser power over 2 W with 10 ns pulse duration has been obtained at a repetition rate of 1 kHz. And the single-axial-mode probability was 100% in one hour without any manual adjustments. The experimental results show that the prelase technique is reliable to attain single-frequency operation.

In order to achieve rapid establishment of long-distance laser communication links, it is an effective program to adopt a GPS / INS integrated navigation system (GINS) for completing the initial pointing of the dynamic laser communication. Firstly, we present a dynamic initial pointing algorithm (DIPA), which can be applied to get the pointing angle (PA) by calculating the real-time data received from GINS. Next, the feasibility of the pointing system is analyzed and the hardware system as well as PC software is designed. Then, experiments in the outdoor are carried out to prove the DIPA. Finally, the correctness and reliability of the pointing system is analyzed.

Based on Z-scan technique, the nonlinear absorption characteristics and nonlinear refraction characteristics of ZnO nanoparticles and ZnO crystal have been studied under the nanosecond (ns) laser pulses and the picosecond (ps) laser pulses respectively. The experimental results show that the nonlinear absorption characteristics of the ZnO nanoparticles and ZnO crystal are reverse saturable absorption mainly due to two-photon absorption under the ns laser pulses. ZnO nanoparticles don’t have nonlinear absorption, and the nonlinear absorption of the ZnO crystal is reverse saturable absorption under the ps laser pulses. The nonlinear refraction characteristics of ZnO nanoparticles are self-focusing under the ns and ps laser pulses respectively, and the nonlinear refractive indexs are 2.14×10^-11 esu, 4.79×10^-13 esu respectively because of bound electron. The nonlinear refraction characteristics of ZnO crystal are self-defocusing under the ns and ps laser pulses respectively, and the nonlinear refractive indexs are -2.2×10^-8 esu, -2.91×10^-11 esu respectively because of free carrier. The experimental results show that ZnO materials can influence the optical nonlinear characteristics, and laser pulse width has little influence on the optical nonlinear characteristics.

Effect of temperature gradient and uniform temperature on tracking performance of reflectors in periscopic laser communication terminals was studied. Zernike polynomials on elliptical area were used to fit wave-front aberration of elliptical reflectors in periscopic laser communication terminals due to temperature distribution. RMS value of the thermal deformation, tracking error and intensity on detectors degradation at receiving terminals caused by thermal deformation were studied in inter-satellite laser communication system. From the result we can know that effect of temperature gradient is the move of peak intensity and a little degradation. The tracking error reaches 2.9μrad when temperature gradient is 14°C/m. The uniform temperature will cause variation of intensity distribution on focus plane of detectors. When the difference between uniform temperature and reference temperature is small, the astigmatism causing by thermal distortion is very important. As the difference becomes bigger, the high-order modes of Zernike polynomials become very important. The distribution of intensity becomes irregular and the area is very big. This will reduce the tracking performance of detectors. This work will contribute to the thermal control of elliptical reflectors in periscopic laser communication terminals on satellites in orbit.

In this paper, we use Z-scan technique to investigate the nonlinear absorption characteristics of water-soluble carbon quantum dots (CDs) that fluorescence emission wavelengths are 450 nm (sample 1) and 550 nm (sample 2) respectively. The nonlinear absorptions of sample 1 and sample 2 are saturated absorption and reverse saturable absorption under the nanosecond (ns) and picosecond (ps) laser pulse. Their nonlinear absorption coefficients are -2.2×10^-10 m/W, 2.1×10^-10 m/W under the ns laser pulse and -2.09×10^-12 m/W, 1.9×10^-12 m/W under the ps laser pulse. The nonlinear absorptions of sample 1 and sample 2 are reverse saturable absorption and saturated absorption under the femtosecond (fs) laser pulse. Their nonlinear absorption coefficients are 8.5×10^-13 m/W and -4.3×10^-13m/W respectively. The experimental results show the signs of nonlinear absorptions for sample 1 and sample 2 are all opposite under the ns, ps and fs laser pulses respectively. The nonlinear absorption of sample 1 results from two-photon absorption. The nonlinear absorption of sample 2 results from two-photon absorption under the ns and ps laser pulses, and single photon absorption under the fs laser pulse. The analyses of experimental results show that the nonlinear absorption characteristics of CDs with different fluorescence emission wavelengths are different. The main reason dues to the different particle sizes of CDs, quantum size effects of CDs influence their nonlinear absorption characteristics.

In recent years , laser guided weapons behave very well at destroying the military goals in the local wars, the single-shot probability, effective range and hitting precision getting better. And the semi-active laser guided weapons are the most widely used laser guided weapons. In order to improve the viability and protect important military goals, it’s necessary to study the technology to against the semi-active guided weapons. This paper studies the working principle, the advantages and disadvantages of the semi-active guided weapons at first, and analyze the possibility of laser angle deception jamming system working. Then it analyzes the working principle and process of laser angle deception jamming technology. Finally it designs a half-real simulation system of laser angle deception jamming, which consists of semi-active laser guided weapons simulation system and laser angle deception jamming system. The simulation system demonstrates the working process of the laser angle deception jamming system. This paper provides fundamental base for the research on the countermeasure technology of semi-active laser guided weapons.

A High Luminance White Light source for Etendue limited application has been demonstrated in this research paper by using blue InGaN laser diode beam over static source of phosphor Ce: YAG layer. Phosphor target has kept static because moving phosphor target light output is not constant and uniform. Different color temperatures had been obtained by varying phosphor concentration and thickness of the layer. When laser beam has focused on phosphor target spot, it induced very high temperature at that spot area. Temperature induced in the layer by laser beam depends on the layer thickness. All the layer thickness, surface temperature, output light flux, efficiency, and light color temperature are interrelate with each other. Uniform laser beam distribution, surface temperature, laser spot size, phosphor layer thickness are successfully calculated. Luminous efficiency, light color temperature, flux, wavelength spectrum, and light output power of laser driven white light source had been successfully observed at different laser beam powers.

Thermal stability technology of signal processing circuit infrared sight is studied under temperature shock. Model parameters and geometry is configured for FPGA devices (EP1C20F400C8), solder material and PCB. Signal circuit boards of full array BGA distribution are simulated and analyzed by thermal shock and waveform through engineering finite element analysis software. Because solders of the whole model have strong stress along Y direction, initial stress constraints along Y direction are primarily considered when the partial model of single solder is imposed by thermal load. When absolute thermal loads stresses of diagonal nodes with maximum strains are separated from the whole model, interpolation is processed according to thermal loads circulation. Plastic strains and thermal stresses of nodes in both sides of partial model are obtained. The analysis results indicate that with thermal load circulation, maximum forces of each circulation along Y direction are increasingly enlarged and with the accumulation of plastic strains of danger point, the composition will become invalid in the end.

The photoelectric detector is a very significance part in laser and its application system, but when photoelectric detector irradiated by high energy laser, the laser may cause thermal damage to the photoelectric detector, when the temperature more than its melting point and vaporization point, there will be a permanent damage in PIN photodetector, leading to the failure of photoelectric detector. In order to study the photodiode damage mechanism by millisecond pulse laser irradiation, a set of experimental system has been built, choosing appropriate pulsed laser parameters to irradiate silicon-based PIN photodiode and monitoring the surface temperature in the process of irradiation, until the PIN photodiode complete failure. The measurement results of real-time temperature, responsivity change and damage morphology were analyzed to conclude the failure reason of the PIN photodiode. The results showed that with the increase of laser energy, the PIN photodiode surface temperature would be also increased accordingly. Before the laser irradiation, the responsivity of PIN photodiode was the same. But after the laser irradiation, the responsivity of the PIN photodiode would be changed and with the increase of laser energy, the decline extent of responsivity would be also increased. Judging from the ablation, crack and fold zone on the surface of PIN photodiode after the laser irradiation, the damage was for thermal stress effect. The continuity of material confined its free expansion. Therefore, the uneven thermal expansion induced the great thermal stress. At the same time, the silicon transited from brittle to ductile and the yield strength dramatically decreased. Once the maximum thermal stress exceeded the critical stress, the plastic deformation and the brittle cracks of silicon would be generated. With the increase of laser energy, the thermal stress damage extent of PIN photodiode would be also increased accordingly and the black area of laser ablation would be also larger. In this paper, the damage mechanism of silicon-based PIN photodiode irradiated by millisecond pulse laser is that the thermal stress causes the phenomena of ablation, fold and responsivity change. The conclusions have a vital significance in improving the performance of PIN photodiode in the field of laser application.

As one of the main weapons, impulse laser rangefinders have become the main object of the electro-optical countermeasures. So its real maximum range (defined as utmost operating range in the paper) becomes the most concerned index to evaluate the performance of electro-optical countermeasure weapons. A method for calculating laser rangefinders′ utmost operating range by its sensitivity in different weather is obtained. Then a method by experiment for getting the sensitivity is supplied. By analyzing the experiment data which the detectivity is 40%-60%, the laser rangefinders′ sensitivity is in the range of 1.7×10^-5 W to 9.8×10^-5 W. For the reason that in order to get an exact utmost operating range, the experiment accuracy of sensitivity is very important, in the last part of paper, the factors which influence the experiment accuracy of sensitivity are analyzed, such as circuit of automatic gain control, the fluctuation of laser power, incident angle of laser.

LADAR echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR, which is designed to simulate the LADAR return signal in laboratory conditions. The device can provide the laser echo signal of target and background for imaging LADAR systems to test whether it is of good performance. Some key technologies are investigated in this paper. Firstly, the 3D model of typical target is built, and transformed to the data of the target echo signal based on ranging equation and targets reflection characteristics. Then, system model and time series model of LADAR echo signal simulator are established. Some influential factors which could induce fixed delay error and random delay error on the simulated return signals are analyzed. In the simulation system, the signal propagating delay of circuits and the response time of pulsed lasers are belong to fixed delay error. The counting error of digital delay generator, the jitter of system clock and the desynchronized between trigger signal and clock signal are a part of random delay error. Furthermore, these system insertion delays are analyzed quantitatively, and the noisy data are obtained. The target echo signals are got by superimposing of the noisy data and the pure target echo signal. In order to overcome these disadvantageous factors, a method of adjusting the timing diagram of the simulation system is proposed. Finally, the simulated echo signals are processed by using a detection algorithm to complete the 3D model reconstruction of object. The simulation results reveal that the range resolution can be better than 8 cm.

High power semiconductor laser is widely used because of its high transformation efficiency, good working stability, compact volume and simple driving requirements. Laser’s lifetime is very long, but tests at high levels of stress can speed up the failure process and shorten the times to failure significantly. So accelerated life test is used here for forecasting the lifetime of 808nm CW GaAs/AlGaAs high power semiconductor laser that has an output power of 1W under 1.04A. Accelerated life test of constant current stress based on the Inverse Power Law Relationship was designed. Tests were conducted under 1.3A, 1.6A and 1.9A at room temperature. It is the first time that this method is used in the domestic research of laser’s lifetime prediction. Applying Weibull Distribution to describe the lifetime distribution and analyzing the data of times to failure, characteristics lifetime’s functional relationship model with current is achieved. Then the characteristics lifetime under normal current is extrapolated, which is 9473h. Besides, to confirm the validity of the functional relationship model, we conduct an additional accelerated life test under 1.75A. Based on this experimental data we calculated the characteristics lifetime corresponding to 1.75A that is 171h, while the extrapolated characteristics lifetime from the former functional relationship model is 162h. The two results shows 5% deviation that is very low and acceptable, which indicates that the test design is reasonable and authentic.

Multiple exciton generation (MEG) is an effect that semiconductor nanocrystals (NCs) quantum dots (QDs) generate multiple excitons (electron-hole pairs) through absorbing a single high energy photon. It can translate the excess photon energy of bandgap (E_g) into new excitons instead of heat loss and improve the photovoltaic performance of solar cells. However, the theories of MEG are not uniform. The main MEG theories can be divided into three types. The first is impact ionization. It explains MEG through a conventional way that a photogenerated exciton becomes multiple excitons by Coulomb interactions between carriers. The Second is coherent superposition of excitonic states. Multiple excitons are generated by the coherent superposition of single photogenerated exciton state with enough excess momentum and the two-exciton state with the same momentum. The third is excitation via virtual excitonic states. The nanocrystals vacuum generates a virtual biexciton by coulomb coupling between two valence band electrons. The virtual biexciton absorbing a photon with an intraband optical transition is converted into a real biexciton. This paper describes the MEG influence on solar photoelectric conversion efficiency, concludes and analyzes the fundamentals of different MEG theories, the MEG experimental measure, their merits and demerits, calculation methods of generation efficiency.

The thermal distortion of silicon reflector irradiated by high-power laser were analyzed by numerical simulation. The results indicate that the contributions from the thermo optic effect, photoelastic effect and deformation are about 97.4%, 0.65%, 1.95% for the transmitted beam. The ratio of thermal distortion between reflected beam and transmitted beam is 0.09.

As an active remote sensing technique, ground-based lidar can detect the backscattered signals of atmospheric cloud and aerosol layers. The measured signals can be used to obtain the vertical profile information of aerosol extinction coefficients. The atmospheric aerosol is measured in Beijing during Asia-Pacific Economic Cooperation (APEC) conference in early November 2014. Fernald method is chosen as the inversion method, and a comparison is made by using Klett’s method. Using the aerosol optical depth(AOD) measured by sunphotometer as a constraint data. The results are used for the analysis of the vertical distribution of aerosol extinction coefficients, three periods are considered, which including several days before, during and after the APEC conference. From the retrieved results of lidar measurement, it was found that the maximum value of extinction coefficients at vertical height in the beginning period reached beyond 2, but it decreased to the range of 0.05 during the conference. Then it gradually increased to more than 2 after the APEC conference. The results show that vertical distribution range of aerosol extinction coefficients decreased to 1km with increasing of AOD. The retrieved AOD results illustrate the extinction characteristics of aerosol，and it relates with the concentration distribution of atmospheric particles. According to the relationship between extinction coefficients and atmospheric visibility, the weather condition can be analyzed.

Hexagonal in-phase coherently coupled arrays of vertical cavity surface-emitting lasers (VCSELs) were fabricated using proton implantation. The arrays showed excellent beam quality with small far-field divergence angle.

In this study, we investigate THz pulses generated from optical rectification with tilted-pulse-front pumping scheme in which the laser beam is focused to a line in a stoichiometric lithium niobate (sLN) crystal. A cylindrical lens and a common lens are used to focus the pump laser beam to a line. The power law of THz pulse generation and the redshift induced from the sLN crystal are measured. The spectral shapes of the laser pulse are changed by inserting a filter into the pump laser beam, causing the THz radiation to change. The filter is a metal wire with 2 mm diameter. Experimental results show that this method can change the generated THz time waveforms but not their spectra. Such method offers a simple means to change and manipulate THz field generated from optical rectification with tiled-pulse-front pumping scheme.

Currently various types of aircraft booming and maturing, however, their long-time navigational capability should be improved urgently. This paper aims at studying laser power beaming, which includes the technology of high-efficient photoelectric conversion and APT(acquiring, pointing and tracking) technology, to provide power for flying UAV(unmanned aerial vehicles) and improve their flight endurance.

The experiment of testing different types of solar cells under various conditions has been done to choose the solar cell which has the highest photoelectric conversion rate and find its most sensitive wavelength. In addition, the charge management module has been chose on the base of the characteristics of lithium batteries. Besides, a laser APT system was designed and set up, at the same time FSM (Fast Scan Mirror) control program and digital image processing program were used to control the system. The success of the indoor experiment of scan-tracking and charging for the moving UAV model via laser proves that this system is workable. And in this experiment, the photoelectric conversion rate of the whole system is up to 17.55%.

Characteristics of coupled-cavity photonic crystal waveguides are analyzed by plane-wave expansion method. By adjusting the radius of the dielectric rods, a linear band in the photonic band structure appears which denotes low group velocity dispersion. Based on the investigations and discussion of the flat band slow light mechanism in coupled-cavity photonic crystal waveguide, flat band low dispersion slow light in coupled-cavity photonic crystal waveguides formed by moving the dielectric rods nearest to the waveguide core is investigated. The waveguide structure with group velocity reduced to zero is demonstrated. Characters of group velocity dispersion (GVD) of slow light are also analyzed, and the magnitude of second-order coefficient of GVD value in the area of ultra slow light is about 10⁵ps²/km, which can guarantee the propagation with efficiency. The novel photonic crystal waveguide can provide various applications, such as optical delay line, optical buffering, all-optical storage and especially in enhanced light-matter interaction both in the linear and nonlinear regime.

High power GaSb based type-I GaInAsSb/AlGaAsSb three quantum wells laser diodes emitting at 2.4 μm were optimized and fabricated. The laser wafer was grown with solid source Molecular Beam Epitaxy System. With optimizations of the epitaxial structure design and the ohmic contact, the operation voltage and the internal loss decreased; the internal quantum efficiency and output power increased. The internal quantum efficiency was determined about 80.1% and the internal loss was 12 cm^-1 by measuring laser diodes with different cavity lengths. An uncoated 2-mm-long laser diode with 90-μm-wide aperture exhibited a threshold current density of 222 A/cm² (74 A/cm² per quantum well), a continuous wave output power of 232 mW and a quasi-continuous wave (1 kHz, 10 μs) output power of 1 W at room temperature.

Time fiducial laser is an important tool for the precise measurement in high energy density physics experiments. The VISAR probe laser is also vital for shock wave diagnostics in ICF experiments. Here, time fiducial laser and VISAR light were generated from one source on SG-III laser facility. After generated from a 1064-nm DFB laser, the laser is modulated by an amplitude modulator driven by 10 GS/s arbitrary waveform generator. Using time division multiplexing technology, the ten-pulse time fiducial laser and the 20-ns VISAR pulse were split by a 1×2 multiplexer and then chosen by two acoustic optic modulators. Using the technique, cost of the system was reduced. The technologies adopted in the system also include pulse polarization stabilization, high precision fiber coupling and energy transmission. The time fiducial laser generated synchronized 12-beam 2ω and 4-beam 3ω laser, providing important reference marks for different detectors and making it convenient for the analysis of diagnostic data. After being amplified by fiber amplifiers and Nd:YAG rod amplifiers, the VISAR laser pulse was frequency-converted to 532-nm pulse by a thermally controlled LBO crystal with final output energy larger than 20 mJ. Finally, the green light was coupled into a 1-mm core diameter, multimode fused silica optical fiber and propagated to the imaging VISAR. The VISAR laser has been used in the VISAR diagnostic physics experiments. Shock wave loading and slowdown processes were measured. Function to measure velocity history of shock wave front movement in different kinds of materials was added to the SG-III laser facility.

Laser induced morphological damage have been observed in silicon-based positive-intrinsic-negative photodiode. This paper adopted the methods of the theoretical calculation and finite element numerical simulation to model, then solved the temperature field and thermal stress field in silicon-based positive-intrinsic-negative photodiode irradiated by multipulsed millisecond laser, and researched the features and laws of the temperature field and thermal stress field. As for the thermal-mechanical problem of multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode, based on Fourier heat conduction and thermoelasticity theories, we established a two-dimensional axisymmetric mathematical model .Then adopted finite element method to simulate the transient temperature field and thermal stress field. The temperature dependences of the material parameters and the absorption coefficient were taken into account in the calculation. The results indicated that there was the heat accumulation effect when multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode. The morphological damage threshold were obtained numerically. The evolution of temperature at the central point of the top surface, the temperature distribution along the radial direction in the end of laser irradiation and the temperature distribution along the axial direction in the end of laser irradiation were considered. Meanwhile, the radial stress, hoop stress, axial stress on the top surface and the R=500μm axis were also considered. The results showed that the morphological damage threshold decreased with the increased of the pulse number. The results of this study have reference significance of researching the thermal and thermal stress effect evolution’s features when multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode, then revealing the mechanism of interactions between millisecond laser and photodiode.

We studied the coating technology, research shows that: to coat the internal structure of coupler we need to consider both intensity problem and heat dissipation problem. For instance: thicker coating will increase the coupler’s resistance to stress and resistance to water vapor, but we will prefer a thinner coating because it is easier to let the light pass though and generate less heat. We’ve tried a number of different coating materials, and analyzed the adhesion during its curing process. Finally, according to the experimental results, we believe that cooling capacity needs to be first considered. Recent experimental results show that we can use advanced coupler coating technology to extend the working life of the coupler. At the end of paper, we provide a coating example and show its real contribution to the working life.

This article analyzes the advantages and disadvantages of a packaging structure for pump coupler, where common heat conduction material is used. In this study, the possibility of using new technology of thermal conductivity is discussed. We also proposes a solution that make the function and effect of package more uniform. A serial of experiments are done for research the cooling effect and the working reliability of the fiber combiners and couplers. Experiment proves that after improved method of package, the cooling speed increases significantly comparing the sample with old type of package technique. The technique discussed in this paper will make the high power fiber laser working long time with steady power output and high efficiency.

The effect of the pump source and the gain fiber on the output properties of ytterbium doped fiber laser (YDFL) work near 980 nm are analyzed theoretically. Base on this analysis, we design a high power all fiberized ytterbium doped laser operating near 980 nm with a core/cladding of 80/130 μm. A 980 nm YDFL experimental setup was constructed, 16.7W 980 nm fiber laser was achieved with an optical-optical conversion efficiency of 32.4%.

Multiple laser communication is the key point of integrated space-ground network system, and it is the necessary prerequisite of realizing the network communication link between multiple satellites. In this paper, current situation and the development status of multiple laser communication are introduced, then optical principles and methods of multiple laser communication are discussed, and advantages and disadvantages are compared and analyzed with different multiple space laser communication system. The systems were classified according to different principles, including the simple principle type, exchange points type, RF and laser combined type, field expanding type and large field communication type. Then we look into the future of multiple laser communication systems, and the result shows that the paraboloid of revolution type has great potential in the future's laser communication space network ,for it’s large communication range and high energy efficiency. It can be used to communicate between the aircraft platform, airship platforms and satellite platforms. Which laid the foundation for the future development of the laser communication space network.

Laser reflection characteristics from the random and rough sea surface are significant for laser detection on the sea surface, and most investigations of which used single-beam laser. However, the single-beam laser spot covers a small area on the sea surface, so that the detection result is influenced seriously by fluctuant sea surface. The application of multiple-beam laser would help to increase the efficiency of laser detection on the sea surface. In this paper, the multiple beams are generated by a single Gaussian beam with the beam splitter. Therefore, all the beams are Gaussian beams and have the same divergence angle with different incident angles and distances. This paper investigates the multiple-beam laser characteristics from the random rough sea surface with geometrical optics method. At first, the fractal method is used to simulate random and rough sea surface. Based on the fractal rough sea surface, the reflection characteristics of each laser beam are calculated with Gaussian beam reflection model on two-dimensional random and rough sea surface, which is derived with geometrical optics method. And then, synthesizing all of the single beam laser reflection characteristics, the multiple-beam laser characteristics from the random rough sea surface can be obtained. With this method, laser reflection characteristics from sea surface of different laser beams are numerical calculated and the comparative analysis of the results is given. Finally, the discussion of some parameters have affections on multiple-beam laser characteristics is also given.

Meso-tetrakis(4-cyanophenyl)N-confused porphyrin [NCTPP(CN)4] and its two metallized derivatives with Cu²⁺ and Zn²⁺ ligand in the central position of the macrocycle are synthesized and spectroscopically characterized. Their excited-state dynamics are investigated with transient absorption (TA) spectroscopy upon excitation by 190 fs laser pulses at 420 nm within their Soret band region. A global and target analysis for the TA spectra of each porphyrin is performed via a four-level model including singlet (S) and triplet (T) states to extract the photophysical parameters at a variety of absorption wavelengths. Furthermore the corresponding excited-state lifetimes are extracted and discussed.

With diode end pumped Nd:YVO₄ and PPMgLN intracavity sum-frequency mixing, a compact, high efficient continuous wave yellow laser at 593.5nm is realized. At an incident pump power of 5.7W, up to 620 mW output power of yellow laser is achieved, the optical-to-optical conversion efficiency is as high as 10.9%.

Laser-induced Surface Acoustic Waves (LSAWs) has been promisingly and widely used in recent years due to its rapid, high accuracy and non-contact evaluation potential of layered and thin film materials. For now, researchers have applied this technology on the characterization of materials' physical parameters, like Young's Modulus, density, and Poisson’s ratio; or mechanical changes such as surface cracks and skin feature like a melanoma. While so far, little research has been done on providing practical guidelines on pulse laser parameters to best generate SAWs. In this paper finite element simulations of the thermos-elastic process based on human skin model for the generation of LSAWs were conducted to give the effects of pulse laser parameters have on the generated SAWs. And recommendations on the parameters to generate strong SAWs for detection and surface characterization without cause any damage to skin are given.

Grating is an important sensor widely used in CNC machine or equipment for length measurement with high precision. Special line scales with dense and micro lines are also widely used for the calibration of length measurement instrument. All the pitches of grating and spaces of dense lines of line scale are needed to be calibrated for a good measurement application. General methods for measurement of dense and micro lines include digital image processing method by CCD Microscope or line scanning method by AFM or SEM, and laser distraction method. There are some disadvantages to measure a long length grating with high precision and efficiently in these methods. A dynamic method based on Photoelectric Microscope is introduced, the lines of grating to be measured is moving uniformly when measuring, and the working distance is a bigger 65mm, the zoom of objective is low 10X. The principle of this dynamic method is discussed and the distortion of line signal is analyzed. The way to decrease the affection caused by distortion of line signal is also described. A special glass grating line scale with length 10mm, space 10μm and width 5μm is measured to verify the method. The measurement result and the uncertainty analysis demonstrate the expand measurement uncertainty (k=2) is less than 0.1μm.

In this paper, an analysis of scattering properties of aggregated particles illuminated by an arbitrary shaped beam is implemented using GLMT. A theoretical treatment for an aggregate of particles illuminated by an arbitrarily incident beam is briefly presented, with special attention paid to the calculation of beam shape coefficients of a shaped beam. The theoretical treatment and the home-made codes are verified by making a comparison between our numerical results and those obtained using a public available T-Matrix code MSTM. Good agreements are achieved which partially indicate the correctness of both codes. Furthermore, some new numerical results concerning the scattered fields of aggregated particles illuminated by a focused Gaussian beam are presented.

Fiber-coupled diode laser pumping source is one of the key components of high-power fiber laser system. Its performance is significant to the output power of fiber laser system. A 1.8kW fiber-coupled diode laser system is designed by using ZEMAX optical design software. The technologies of high-precision beam collimation, spatial multiplexing, polarization multiplexing, beam expanding, focusing and coupling are used to couple the beams of 42 diode laser bars into a fiber with a core diameter of 200μm and NA 0.22. Every beam emit from diode laser bar is single polarization, and its central wavelength is 976nm @ 55W. The desigh result showed the fiber output power could reach 1800W, and the fiber-coupling efficiency was 78%, the brightness was 37MW/（cm²·sr）,corresponding. This fiber-coupled system can be used in fiber pumping, material process and many other areas.

This paper has investigated and designed a multi-channel laser focusing transceiver system based on the combination of the laser technology, the space technology and the modern photoelectric detection technology which has the feather of wide wave band, non-chromatic aberration and high quality of image quality etc. The system could be synchronized and can change the distance of detection in a particular direction and obtain the image of atmospheric echo signals at different distances. In this paper we established a multi-channel and variable range laser focusing transceiver system that consists of a single-channel laser focusing transmitter system and a dual-channel receiving telescope system. The three channels of the system depend on the same reference axis. We propose a new method that is capable to improve the laser focusing transceiver system performance. The method is implemented by using parabolic reflector design in the primary and secondary mirror of the variable range laser focusing transmitter system, dual-channel off-axis design in the receiver system and simultaneous imaging design in the different regions of the same CCD target surface of the subsequent imaging system. The detection by two channels using off-axis design would be convenient for computing follow up information. On the base of theoretical basis of the reflective double mirror system and the theory Gaussian beam propagation, this paper calculates the actual converging sot size of the transmitter system and analyzes the wavefront aberration the defocus incidence. The oblique incidence will introduce the certain astigmatism and a small amount of coma and the defocus incidence will produce the certain coma and a small amount of spherical aberration and astigmatism. Finally, an experimental multi-channel laser focusing transceiver system was established and the image quality of the transceiver system on the base of wavefront aberrations, the spot diagram and the MTF curve of some fields is analyzed. Through a lot of experiments, the actual test results are obtained. The wavefront aberrations RMS of the system are 0.079λ,0.0822λ,and 0.0808λ,respectively. The actual test results of the system have met the design requirements which must be better than λ/12=0. 0833.

Atomic magnetometer which uses alkali atoms as the sensors can realize ultrahigh sensitivity magnetic field measurement and has extensive applications scientific researches. Semiconductor lasers are used as the pump and probe laser in atomic magnetometer. Due to structural characteristics of semiconductor laser, beam divergence angles in vertical and horizontal direction have large deviation and laser beam diverges extremely fast. However, poor laser beam affects the implementation of atomic magnetometer sensitivity adversely. Only the circular laser beam with Gaussian distribution guarantees the homogeneous polarization of alkali atom vapor and high efficiency of atomic magnetometer. Consequently, a beam collimation system must be designed. In this paper, a collimation method using a thin lens and a pair of anamorphic prisms is proposed to guarantee the laser spot size approximately constant. The thin lens is used to decrease fast-axis divergence angle and ensure transmitted light is parallel. The anamorphic prisms pairs expand the laser beam in slow-axis and make the beam spot nearly round. Initially, the effect of thin lenses and anamorphic prisms on the relationship of input and output beam profiles is theoretically analyzed based on principle of geometrical optics. Then the software Zemax is used to simulate the collimation system. Finally, a beam collimation system is designed and tested. The experiment result shows that the laser beam size is approximately 2×2cm² and the beam approximate a Gaussian profile, which can meet the requirement of the atomic magnetometer.

A diode-pumped alkali laser (DPAL) provides the significant promise for high-powered performances. For an end-pumped DPAL, both the absorption and the lasing distribution crucially affect the output physical features. In this report, a mathematical model is introduced for examining the absorption and lasing processes of the gas-state media by using a segmental approach. The energy transmission inside the oscillator has been theoretically analyzed for construction of a reciprocating regime which is based on the self-consistency principle. Basically, the conclusion can be extended to any end-pumped laser configurations.

Diode-pumped alkali lasers (DPALs) have gained rapid development in the recent years due to their great potential for realization of high-power lasers. Relaxation oscillation (RO) is a common phenomenon related to the dynamic process in time domain. Generally, the generation of spikes in RO may affect the output stabilization of a DPAL. In this paper, we develop a kinetic model to investigate the output characteristics in time domain. Using such a mathematical model, a comparative study on the RO features of a diode-pumped rubidium vapor lasers (DPRVL) and a diode-pumped cesium vapor lasers (DPCVL) is theoretically carried out with different physical parameters including the cell temperature, buffer gas pressure, pumping power and reflectance of an output coupler. The analyses should be valuable for design of a steady high-powered DPAL.

Diode-pumped alkali lasers (DPALs) have attracted a lot of attentions in the recent years for their high Stocks efficiency, good beam quality, compact size and near-infrared emission wavelengths. In this study, we analyze the thermally-induced lens in an end-pumped cesium cell by using the evaluated parameters such as the population density distribution, the transition rates of pump photon absorption, and the transition rates of laser photon emission, which had been obtained in our previous study. After dividing a cylindrical vapor cell into many cylindrical annuli, we calculate the refractive index n and the thermal-optic coefficient dn/dT in every annule. And then, we carry out the ray-trace to describe the propagation of an incident ray inside the vapor cell. Assuming that the incident plane-wave has a flat-top distribution, the intensity distribution of the outputted beam can be deduced. We adopted the second-moment calculation to evaluate the beam size after the ray passes through a pumped cell. Finally, the effective focal length of a thermally-induced lens was obtained for the end-pumped laser configuration. The research will be helpful to improve the beam quality of a DPAL.

To assess the potential application of terahertz waves in security examination, the transmission characteristics of terahertz waves in packaging materials should be studied. This paper simulates the propagation of terahertz waves in cloth and paper, studies the changes of shape and position of crest of terahertz waves before and after these materials, and gets the law of these changes, which has potential applications in thickness measurement for the thin insulated materials; gives reflected and transmitted wave of terahertz waves, and computes reflected and transmitted coefficient, indicates the good transmission properties of these materials for terahertz waves, which provides the theoretical basis for the realization of contactless security examination of packaged post, package and people pass the important passageway (such as airport and station).

Space broadband network based on laser link represents the future development direction, Europe, the United States, Japan and other space powers have been researching the theory of space laser communication and the key technology constantly, and have carried out the key technology test of inter-satellite laser communication and satellite-ground laser communication on orbit. However, what is the technology system of space broadband network based on laser link? up to now, it is still controversial, such as wavelength, coding, and modulation mode, exchange mode and so on. Here, by analyzing all kinds of space laser communication test and its technology parameters, combined with the application requirement of space broadband network, a set of technology system for space broadband network based on laser link is put forward, although just a preliminary research result. At first, this paper introduces the basic conception of space broadband network based on laser link, defines the space laser broadband network technology system and its research scope. Then analyze the main contents of space laser broadband network technology system, especially the technical route choice involved, and by studying, the related suggestions are given. Finally, with the development of space broadband network, the issue of standardization in space laser communication technology system is put forward, in order to cause attaches great importance to scientific research institutes and relevant experts.

It is always an attracting research field for the interaction between laser and matters. The interaction between laser and matters is used not only in the natural science, but also in practical application, for example, laser machine, laser weapon, laser ablations and so on. In this paper, we will give the model for the damage effect of the composite materials caused by the superpower laser weapons. Mechanism of the laser damage on the composite materials have been researched and modeled by the numerical analysis methods. Through the designed model, we analyzed the temperature and the stress fields of the composite material after the superpower lasers attacks with different power densities. By analyzing these modeling results, we achieved some conclusions on the threats to the composite materials from the superpower lasers. From the results, we have obtained the Irradiated threshold from the Laser. This paper will provide the theoretical foundations for the anti-laser design of the composite materials.

Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument’s FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

Most methods to research thermal effect are based on the analytical method, but he calculation processing is too complex, and we can get analytical solution only in a very small number of simple cases. We research the issue by use of finite element method (FEM). In this paper, the main research areas are as follows: The first, a theoretical mode of pulse laser leading to thermal stress damage of dielectric material is developed. Based on this theoretical model, transient distributions of temperature field and thermal stress field are analyzed by finite element method (FEM). The FEM method involves element discretion, element analysis, and overall analysis. Transient temperature field and stress field are simulated by using FEM software. Numerical results indicate: There is large temperature gradient in radial directions, while small temperature gradient exists in axis directions, and central temperature will be higher as power density of laser is higher. The results demonstrate that thermal stress damage is critical and circumferential stress play a main role in damage mechanism, the principle and methods of film measurement are summarized, the results in this paper may provide theoretical base for further research.

The carrier generation in high gain GaAs photoconductive semiconductor switches (PCSSs) is researched. Based on the "electron avalanche domain (EAD)" ideas, the physical process of carrier generation is explained. This analysis supports the current filaments velocities that can exceed the value of 2 × 10⁹ cm/s. The results of this theoretical investigation are consistent with those of the reported experimental observations.

A numerical method is proposed for the transport of infrared radiation in participating medium. The method is implemented using the Finite Volume Method (FVM) for solving the radiative transfer equation (RTE), and Mie theory for computing the absorption and scattering characteristics of the medium. The advantages of the method reflected in two aspects. On the one hand, the radiative characteristics is got from a data base established in advance using Mie theory, on the other hand, the scattering phase function is simplified by distinguishing the "forward average scattering" and "other directional average scattering". Both the two procedures yield significant computational savings with little loss in accuracy for predictions of spectral and total transmission.

In the high-power laser facility, frequency modulation to amplitude modulation (FM-to-AM) effects has seriously affected the power balance between beams and restricted the laser flux levels of safe operation in the system. For FM-to- AM effects produced by gain-narrowing effects, according to the amplifier gain-narrowing function model, after simulating and analyzing the properties of FM-to-AM effects, a corresponding compensation function is designed. Using sinusoidal compensation function, with the use of a birefringent crystal and liquid crystal modulator, adjusting the crystal angle in the range of 45 °, the center wavelength could be reduced in the magnitude of the range from 0 to 30dBm. By changing the voltage of the liquid crystal, the center wavelength could be adjusted within 1051.5-1054.5nm freely. For the regenerative amplifier with the gain of 70dB and input center wavelength of 1053nm and bandwidth of 0.7nm, the output FM-to-AM magnitude could be controlled within ~11% by this compensation system.

For solving the problem of dispersion in fiber communication, this article designed a ultra large negative dispersion regular octagonal PCF with liquid infiltration. The effects of air-hole diameter (d), layer-to-layer spacing (Λ) and refractive index of the infiltrating liquid (nL) on dispersion have been obtained based on Finite Element Method (FEM) by using COMSOL Multiphysics. The results show that with an increase of nL, the dispersion gets blue-shifted and the negative dispersion will increase. However, with the increase of Λ, the dispersion is red-shifted and the negative dispersion will reduce. Again, with the increase of d, the dispersion is red-shifted but with an augment of negative dispersion. This paper’s theoretical study shows a high negative dispersion of -13000ps/(nm·km) around 1550nm when d=1.000μm, Λ=1.500μm and n_L=1.374. The Dispersion Compensating Fiber (DCF) can effectively compensate the single mode fiber G. 652, which has been widely used. One meter the DCF can compensate 650 meters G. 652.

The fiber laser has very obvious advantages and broad applications in remote welding, 3D cutting and national defense compared with the traditional solid laser. But influenced by heat effect of gain medium, nonlinear effect, stress birefringence effect and other negative factors, it’s very difficult to get high power linearly polarized laser just using a single laser. For these limitations a polarization-converting system is designed using beam shaping and combination technique which is able to transform naturally polarized laser to linearly polarized laser at real time to resolve difficulties of generating high-power linearly polarized laser from fiber lasers in this paper. The principle of the Gaussian beam changing into the hollow beam passing through two axicons and the combination of the Gaussian beam and the hollow beam is discussed. In the experimental verification the energy conversion efficiency reached 93.1% with a remarkable enhancement of the extinction ratio from 3% to 98% benefited from the high conversion efficiency of axicons and the system worked fine under high power conditions. The system also kept excellent far field divergence. The experiment phenomenon also agreed with the simulation quite well. The experiment proves that this polarization-converting system will not affect laser structure which controls easily and needs no feedback and controlling system with stable and reliable properties at the same time. It can absolutely be applied to the polarization-conversion of high power laser.

A scheme is proposed to obtain slow light in a coulped quantum wells microcavity with tunneling induced transparency between intersubband electronic transitions. Three prolaritons are created by intracavity Fano interference between fundamental mode photon and two quantum oscillators of coherent subband electronic excitations. A narrow middle dark polariton of the three can be produced, which can be used to suppress the line profiles of the transmission or reflection spectra for the incident light. This leads to slow propagation of the incident light in the microcavity. The semiconductor optical microcavity can be an alternative choice of quantum photoelectronic devices in nanoscale.

Nowadays LADAR system set on practical moving platform is purposed to detect real-time velocity as well as precise distance and direction evaluation for safe landing or obstacles avoiding. On account of narrow band, brief algorithm, non-modulated CW Doppler LADAR based on optical heterodyne principle could acquire the velocity of multiple targets with high frame frequency, high SNR ratio while no velocity ambiguity. In this paper, a non-modulated 1064nm CW Doppler fiber LADAR system with high frame frequency as well as high velocity precision is proposed. The experimental result of the system shows a velocity precision of 6.65mm/s, and a velocity detection frame frequency of 20FPS, which essentially meet the practical demands.

Coherent combining of several multi-wavelength fiber lasers is a promising approach to suppress the nonlinear effects and improve the output power. Passive phase locking of two multi-wavelength fiber lasers has been demonstrated by using mutual injection coupling and spatial filtering technique, and the effect of feedback elements on the phase locking properties has been investigated in detail. Three different kinds of feedback elements, fiber Bragg grating (FBG), fiber loop mirror (FLM) and fiber reflection mirror (FRM) are employed as the component laser’s high reflection mirror to construct the phase locking array respectively. Compared with the traditional feedback element FBG, the FLM is made of a 3dB fiber coupler and provide high reflection feedback in a wide spectral range for fiber laser, and the FRM is also a wide-band reflector with the fiber end coated by multilayer dielectric film. When the FLM and FRM are employed as the component laser’s feedback elements, a large number of longitudinal modes operate simultaneously and the spectra vary continuously. Fortunately, stable phase locking has been obtained as long as the single-mode filtering fiber is introduced into the feedback loop, and obvious interference patterns with high fringe visibility have been observed in far field. The phased array’s output power can also keep stable at the same time, and its amount is higher than the case of using FBG. In conclusion, the research results indicate that efficient phase locking of several multi-wavelength fiber lasers can also be achieved by passive self-adjusting method and higher output power can be obtained compared with the usual coherent combining of narrow-band laser beams, as long as necessary optical coupling is introduced among component lasers and proper spatial filtering measures are adopted.

In recent years, the distributed Bragg reflector (DBR) laser diode (LD) has advantages of its small size, high efficiency, low power consumption and so on, so it has been widely used in precision measurement, optical information processing, quantum research and other fields. There is a strict requirement for the output frequency of the DBR laser diode in precision measurement technology. Therefore, controlling the frequency of the laser accurately is of great significance for precision measurement. Currently, there are a lot of frequency control scheme for laser diode, mainly through the external system to stabilize the frequency of laser diode, the drawback of which is that it is not conducive to system integration. Therefore, this paper proposes a method based on FPGA for controlling the output frequency of the laser diode. The main purpose of the control is to study the frequency characteristics of the laser diode. In this paper, the FPGA chip is used as a micro controller, and combined with PID control algorithm constitute a closed loop control circuit. At the same time, the control algorithm is programmed into the FPGA device, which can maximize the operating speed of control system. For different frequency of the laser, it is only required to modify the control parameters simply, which can be realized the steady control of the light source. Through the test, near the operating temperature of the laser diode, temperature stability is better than ±0.01°C. As a result, the laser frequency stability can be controlled to 0.1%.

For correction of Abbe error in involute gear measurement, a laser interferometric measuring system is applied, in this system, the laser beam is split into two paths, one path is arranged tangent to the base circle of gear for measurement of profile, another path is arranged parallel to the gear axis for measurement of helix, two cube-corner reflectors are attached at the end of probe stylus closing to the tip, by this approach, the length offset between probe tip and reference scale is minimized , finally, the Abbe error is decreased. On another hand, the laser measuring error is caused by bending of stylus, the mathematic relationship between amount of bending and probe deflection is deduced. To determine the parameters in this mathematic relationship, two sizes of stylus are used for experiments. Experiments are carried out in a range of ±0.8mm for probe deflection. Results show that the amount of stylus bending is linear with deflection of probe, the laser measuring error caused by stylus bending will be smaller than 0.3μm after correction.

In this paper, a photonic crystal (PC) pattern, using ellipse rods as the lattice point, is proposed to improve the absorption properties of the VO₂ film. We set up a numerical model for the 2D PC patterned film and simulated the transmission property with Finite Difference Time Domain (FDTD) method. The optical absorption is achieved in near infrared by exacting Bloch mode at photonic band edge coupling the incident light from the free space to the large area resonant photonic band edge modes. The numerical simulation shows an obvious enhancement and the overall absorption is 26%. Moreover, we give a further study of the PC patterned film. Different polarization angle of light source and structure parameters are applied to study the polarization property of the film. The film shows discrepant absorption, thus the polarization control using this film can be realized further.

Nuclear magnetic resonance gyroscope (NMRG) is the smallest atomic sensor in navigation level. Spin precession can be detected by measuring the optical rotation of the plane of an off-resonant linearly polarized probe beam. The optimal frequency and power of the probe beam counts for the performance of NMRG, which has been verified by our former experiments. The NMRG system would have higher sensitivity and lower consumption comparing to the circularly polarized probe beam. In this paper, we demonstrate the optimal frequency and power of an off-resonant linearly polarized probe beam by theoretical analysis and experimental verification. In theory, the off-resonant linearly polarized probe beam can be decomposed into two circularly polarized components of opposite helicity. Its plane of polarization will be rotated by an angle, due to the positive and negative helicity light experience different induces of refraction as it propagates through a birefringent medium. The off-resonant linearly polarized probe beam becomes partially absorbed by the alkali vapor as it propagates through the NMRG cell. The overall signal is determined by both optical signal and beam absorption. After optimizing the frequency and power of the probe, the magnetic field sensitivity was 2pT/Hz^1/2.

The laser intensity stability counts for the performance of Nuclear Magnetic Resonance Gyroscope (NMRG). We switch to attenuate the fluctuation of laser intensity with the aid of an opto-electric modulator and feedback control. The Liquid Crystal Variable Retarder (LCVR) has a sharp edge over its counterparts such as AOM and EOM benefiting from its compact size, low operation voltage and large clear aperture. In this paper, we demonstrate a LCVR based laser intensity stabilization system designed for a NMRG prototype. The setup mainly compromises of two crossed linear polarizers, a LCVR, a polarized beam splitter, a photo detector and a digital servo control unit. The intensity of a small portion of laser split by the PBS is detected by the photodiode and then fed into the servo control unit. It compares the current laser intensity with the setpoint value, generates a proper control signal under the supervision of the built-in algorithm and drives the LCVR to change the incident laser polarization state, and hence the output laser intensity. In addition, we derive the formula of the relative output laser intensity with voltage, which helps to design the control algorithm. Finally, the long-term stability of the system reaches 0.038% in a 4-hour continuous measurement.

Hyperspectral Lidar using supercontinuum laser as light source, applying spectroscopic technology gets backscattered reflectance of different wavelengths, and can acquire both the geometry and spectral information on the target. In the vegetation detection by using Hyperspectral Lidar, through refusing 3d and spectral data, we can get the physical structure and biochemical parameter such as vegetation index, chlorophyll content. This paper constructs a simulating scene including an atmosphere, vegetation and ground surface, simulates spectral waveform of different input conditions such as varying ground reflectance, sloped versus flat ground, and comparisons of "leaf-on" and "leaf-off" conditions. First, using fractal method, the vegetation model was established. Second, applying Monte Carlo method, the laser between vegetation was traced. Third, using the PROSPECT model, established the vegetation spectral reflectance model. Last, by combining of the above three models, built hyperspectral Lidar vegetation detection model, and carry out simulation model under a variety of conditions supply.

ICESat-2 is the successor to NASA’s ICESat (Ice, Cloud and land Elevation Satellite) mission scheduled to be launched in 2018. The new photon counting LiDAR onboard ICESat-2 introduced new challenges to the estimation of biomass and its dynamics, especially for the abundant photon noise in the atmosphere and below the ground. In order to remove the ambient noise and get a better detection of the canopy and the ground, this paper establishes an approach to identify potential signal from ambient noise automatically. The framework is based on the classic geodesic active contours method. Previous studies have suggested that this technique is very sensitive to initial contour, so we adopted NASA’s surface-finding algorithm to get the expected initialization for contour evolution. Observations from MABEL (Multiple- Altimeter Beam Experiment LiDAR), which is the ICESat-2’s high altitude airborne demonstrator, were used to validate this approach. The results showed that the potential signal photons were about 22% among the whole photons compared with about 78% background noise even in the night flight situation. The signal-to-noise ratio is expected to be smaller in the daytime flight situations, making it more difficult to distinguish the canopy. The results demonstrated that this technique can identify the potential signal photons effectively with error rate less than 4.2%. The proposed approach is appropriate for the present airborne simulated data with a high accuracy for flat surface with dense canopy. Future work will be focused on the stability and general applicability of this approach over large areas and different ground surfaces.

In this paper, on the basis of the theory of quasi phase matched, CO₂ laser spectrum corresponding to GaAs chip within the scope of the matching length was calculated. Through the numerical solution of the wave equation, the relationship between power density of pump laser and frequency doubling conversion efficiency was given under the different crystal length conditions. By adjusting the CO₂ laser gas mixture components, we optimized the pump laser pulse wave to meet the requirements in the temporal distribution of the pump light. On the other hand, we optimize the output beam mode to meet the pump light distribution in space requirements. We use the tunable TEA CO₂ laser as the light source to pump quasi phase matching GaAs crystal, When the pump wavelength is changed from 9.23μm to 10.75μm range, the conversion efficiency of frequency doubling output is greater than 4%, when the pump wavelength is 10.68um, the frequency doubling efficiency reached 6.58%.

With the development of big data and information globalization, the requirements of massive information transmitting and sharing among data centers are expanding, especially among those data centers which are extremely far away from each other. In the above field, conventional optical fiber transmission faces many problems such as complex networking, poor security, long node switching delay, high lease and maintain cost and low migration flexibility. Besides, in the near future, data centers may tend to be built in the remote Polar Regions or on the sea for natural cooling. For the above situation, sharing the massive information among global data centers based on satellite laser communication is proposed in this paper. This proposal includes advantage analysis, research of restraining atmosphere interference, etc. At last, by comparison with conventional technology, the research result shows that massive information transmitting and sharing among global data centers based on satellite laser communication has far reaching application potential.

The supercontinuum produced by photonic crystal fibers has a very wide spectral width and good flatness, and it makes the applications of supercontinuum greatly expanded in many areas. However, due to the two-dimensional special structure of photonic crystal fibers and the complex nonlinear effects in supercontinuum generation, a specific kind of supercontinuum is not often easily to be obtained, so it makes the simulation of supercontinuum generation become very important. The widely used split-step Fourier method for solving nonlinear Schrödinger equations to simulate supercontinuum generation can not achieve a very high precision, because the high order nonlinear effect is often ignored and the nature of the algorithm also has an impact on the accuracy. So a high precision single step algorithm called Runge-Kutta method which is widely used for engineering is mentioned in this paper. Taking the higher-order nonlinear effects in supercontinuum generation into consideration, a more accurate and efficient calculation method of supercontinuum simulation is given by solving the generalized nonlinear Schrödinger equation. Simulation on the supercontinuum generation in photonic crystal fiber has been made. While the incident laser pulse with the 120fs pulse width and the 800nm center wavelength transmits in a period of photonic crystal fiber, the supercontinuum that covers the wavelength from 500nm to 1100nm is generated. The flatness of the spectrum will get some improvement with the increase of the incident pulse’s peak power.

The laser performance and thermal analysis of Nd:KGW laser continuously pumped by 808 nm and 877 nm are comparatively investigated. Output power of 670 mW and 1587 mW, with nearly TEM₀₀ mode, are achieved respectively at 808 nm pump and 877 nm pump. Meanwhile, a high-power passively Q-switched Nd:KGW/Cr⁴⁺:YAG laser pumped at 877 nm is demonstrated. An average output power of 1495 mW is obtained at pump power of 5.22 W while the laser is operating at repetition of 53.17 kHz. We demonstrate that 877 nm diode laser is a more potential pump source for Nd:KGW lasers.

Thermomechanical behaviour of a glass/epoxy composite plate under local laser irradiation is investigated. Physico-chemical transformations and gas transport in a matrix and fibers are describe by Arrhenius and Darcy's law. The changes of material thermal properties are expressed in terms of the volume fractions of fiber, resin, gas and char. At the same time, we take into account the effects of pore pressure and elevating temperature on thermal stresses and strains. It is established that transverse stress, radius stress and interlayer shear caused by local heating and pore pressure are causes of delamination and cracking of composite plates under laser heating. And interlayer shear can lead failure of composite fast.

In order to improve the dynamic tracking performance of coarse tracking system in space optical communication, a new control method based on active disturbance rejection controller (ADRC) is proposed. Firstly, based on the structure analysis of coarse tracking system, the simplified system model was obtained, and then the extended state observer was designed to calculate state variables and spot disturbance from the input and output signals. Finally, the ADRC controller of coarse tracking system is realized with the combination of nonlinear PID controller. The simulation experimental results show that compared with the PID method, this method can significantly reduce the step response overshoot and settling time. When the target angular velocity is120mrad/s, tracking error with ADRC method is 30μrad, which decreases 85% compared with the PID method. Meanwhile the disturbance rejection bandwidth is increased by 3 times with ADRC. This method can effectively improve the dynamic tracking performance of coarse tracking and disturbance rejection degree, with no need of hardware upgrade, and is of certain reference value to the wide range and high dynamic precision photoelectric tracking system.

Broadband mid-infrared lasers are desirable for pretty important applications in fields of environmental protection, medical treatment, military applications, scientific, and other domains. Recently, super-continuum laser sources have achieved striking development. However, limited by the substrate materials, the output power scaling of the broadband mid-infrared fiber laser sources could not be increased drastically, especially for the long wavelength region. In this paper, we reported an experimental study about the broadband mid-infrared lasers based on Cr2+ doped II-VI ceramic materials, by using of a super-continuum laser source developed by our groups operating at 1550~2130nm with 200mW output power. The result suggested that the near-infrared spectral component of the super-continuum source was deeply absorbed by transition metal doped zinc chalcogenides ceramic materials, meanwhile the mid-infrared part, however, had been enhanced significantly by this new "power amplifier." Actually single-pass amplification efficiency was very limited. The best way to solve this problem was multi-pass amplification systems. We had shown an initial proof of this assumption by a double-pass experiments, the result was consistent with expected effect. Above all, the spectrum shaping from short wavelength to long wavelength was obtained. The innovative discovery had laid a solid foundation for high power, high efficiency, broadly tunable mid-infrared solid state lasers.

The third-order nonlinear optical response of molybdenum disulfide dissolved in ethanol was investigated using a modified time-resolved pumpeprobe measurement with phase object at 532 nm with pico-second laser pulse. The experimental results clearly indicate that the observed nonlinear response should be of excited-state origin. The compound exhibits strong saturable absorption and long excited-state lifetimes. The nonlinear absorptive and refractive parameters of the phenoxazinium salt were evaluated by combination of picosecond pumpeprobe measurements and picosecond Z-Scan experiments. The experiment results demonstrate this compound is a promising nonlinear optical material.

A large-aperture Nd:YLF thin disk laser oscillator is demonstrated, in which the refractive index matching liquid is used as the coolant flowing in narrow channels to cool the multiple thin disks directly. A high uniformity of pump intensity distribution is realized by using waveguides. With the a-cut Nd:YLF thin disks at different doping levels, a linearly polarized laser with the maximum output energy of 346 mJ is achieved with the repetition of 350 Hz, corresponding to an optical-optical efficiency of 8.7%, and a slope efficiency of 10%. The beam quality β factor is estimated less than 8 in the horizontal direction due to the positive branch confocal unstable resonator. To the best of our knowledge, it is the first time that the direct-liquid-cooled Nd:YLF thin disk unstable resonator is reported.

We report on the generation and propagation of stretched-pulse in an erbium-doped fiber laser with near-zero dispersion. The pulse exhibits broadband spectrum with sidebands on long-wavelength side, which may be attributed to the strong gain and loss perturbations induced by the long cavity. After the extra-cavity propagation via a 19-m single-mode fiber (SMF), the spectrum of pulses almost keeps unchanged whereas the pulse duration broadens from 0.22 to 6.33 ps, indicating that fiber dispersion plays a key role in pulse propagation. Moreover, the evolution of pulse duration in SMF is in good agreement with that of theoretical predictions. This pulse evolution through extra-cavity fiber is quite different from the evolution of dissipative solitons, in which the pulses are compressed rather than broadened.

In this paper, we investigate the nonlinear optical properties of unsymmetrical trimethine cyanine dyes(ethyl-4-(3-(3-ethylbenzo[d]xazole-2(3H)-ylidene)prop-1-en-1-yl)quinolin-1-iumiodidebenzo[d]xa zole group) by conducting Z-scan technique at 532 nm and time-resolved pump probe with phase object (POPP). Pronounced reverse saturable absorption (RSA) and positive refraction are observed. Moreover, the relevant third-order NLO photo-physical parameters of unsymmetrical trimethine cyanine dyes determined unambiguously.

We described a widely tunable intracavity continuous-wave singly resonant optical parametric oscillator (SRO) through a minimal laser diode end-pumped Nd:YVO₄ laser. Laser source from 1.9μm to 2.4μm is obtained by temperature tuning of the 32.2μm period periodically poled MgO:LiNbO₃(PPMgLN) crystal. The maximum power, 0.84W signal wave at 1.966μm and 0.56W idler wave at 2.319μm, are simultaneously obtained at 5.5 W of input diode power. The corresponding conversion efficiency are 15.2% and 10.2% respectively, so the whole efficiency is more than 25%. This allows the development of practical infrared cw SRO’s using compact, widely available, low-cost laser pump sources.

The simulation of light waves propagating in fibers oppositely has to handle the extremely huge volume of data when employing sequential and unidirectional methods, where the simulation is in a coordinate system that moves along with the light waves. Therefore, alternative simulation algorithm should be used when calculating counter propagating light waves. Parallelizable and bidirectional (PB) algorithm simulates the light waves matching in time domain instead of space domain, does not need iteration, and permits efficient parallelization on multiple processors. The PB method is proposed to calculate the propagation of dispersing Gaussian pulse and a bit stream in fibers. However, PB method also has apparent advantages when simulating pulses in fiber laser amplifiers, which has not been investigated detailed yet. In this paper, we perform the simulation of pulses in a rare-earth-ions doped fiber amplifier. The influence of pump power, signal power, repetition rate, pulse width and fiber length on the amplifier’s output average power, peak power, pulse energy and pulse shape are investigated. The results indicate that the PB method is effective when simulating high power amplification of pulses in fiber amplifier. Furthermore, nonlinear effects can be added into the simulation conveniently. The work in this paper will provide a more economic and efficient method to simulate power amplification of fiber lasers.

Considering the axially symmetric polarization and intensity distribution, radially polarized (RP) laser beam has comparatively higher axial component of electric field and smaller size of focal spot compared to linearly polarized (LP) laser. In this study, the effect of radial polarization on multiphoton fabrication has been studied, and polymer spots and lines are chosen as the study objects of 2D micro/nano structures of multiphoton lithography. These structures were fabricated with IP-L, a commercial negative photoresist, by RP fs-pulse laser beam which was tightly focused by an objective lens with high numerical aperture. Multiple experimental conditions, such as fabrication power, exposure time and scanning velocity, were verified in order to observe the structural variation of these polymer structures. On the basis of measurement from images of the scanning electron microscope, the transverse and longitudinal sizes of polymer spots and lines could be analyzed, and the relationship between the aspect ratio (AR) and the above experimental conditions could be acquired. The statistical results agree with our predictions that the RP laser beam can significantly reduce the AR, and the AR in RP laser fabrication has little correlation with conditions besides fabrication power, such as exposure time and scanning velocity.

The photonic band gap effect which originates from the translational invariance of the periodic lattice of dielectrics has been widely applied in the technical applications of microwave, telecommunication and visible wavelengths. Among the various examples, polymers based three dimensional (3D) photonic crystals (PhCs) have attracted considerable interest because they can be easily fabricated by femo-second (fs) ultrafast laser direct writing (DLW) method. However, it is difficult to realize complete band gap in polymers PhCs due to the low index contrast between polymers and air. Here, we report the design and experimental realization of light's nonreciprocal propagation in woodpile PhCs fabricated with DLW method. Firstly, we fabricated several polymers woodpile PhCs on glass substrate with different crystal planes. The Fourier transform infrared spectroscopy (FTIR) measurements are in agreement with the theoretical predictions, which proves the validity and the accuracy of our DLW method. Further measurements of the transmission spectra with respect to the incident angle reveal that the surface crystal planes and incident wave vectors play important roles in the optical response. Furthermore, we designed and fabricated a 30° PhC wedge. And we find nonreciprocal transmission effect between the forward and backward waves, resulting from the nonsymmetrical refraction of the light in different planes. Our results may find potential applications in future 3D photonic integrated circuits and pave the way for the fabrication of other photonic and optical devices with DLW method.

The spot profile and intensity distribution of output beam from unstable resonator of a DF Laser were measured. The results showed the spot was a ring with 45mm external diameter and the measurement data sufficed for the design requests. But the spot was asymmetric seriously on horizontal direction, which was arose by two possible reason, one was non-uniform distribution of the gain medium , the other was the optic-axis migration to upstream of gain medium.

In order to further increase the fiber-coupled module output power, eight cm-bar 808 nm laser diodes, 50 w output each, fiber coupling module has been designed by using ZEMAX optical design software through space and polarization beam combination method. The core diameter of output fiber is 400 μm with a numerical aperture of 0.22. Finally the fiber output power is 350.2 W, with a coupling efficiency of 87.6%.

Based on the Fresnel-Kirchhoff diffraction integral and Fourier transform, the propagation equation and its Fourier spectrum for ultra-short chirped pulsed Gaussian beams diffracted by Gaussian aperture are derived in dispersive medium, and the frequency-domain analytical electric field are presented. The effects of relative aperture, transmission distance and chirp parameter on the axial spectral properties are illustrated with numerical calculation results, and the variations of off-axis power spectrum with relative aperture, transmission distance and off-axis radius are given. It is found that the axial power spectrum of ultra-short chirped pulsed Gaussian increases with increasing relative aperture, the axial spectral blue-shift increases and approaches an asymptotic value associated with chirp parameter and propagation distance. The axial spectra of ultra-short chirped pulsed Gaussian become broadened with increasing the absolute value of the chirp parameter. With increasing off-axis radius, the off-axis power spectrum reduce rapidly, and the distribution of spectra shifts to the left. The off-axis spectral redshift increases with increasing off-axis radius.

The optical component of photoelectric system was easy to be damaged by irradiation of high power pulse laser, so the effect of high power pulse laser irradiation on K9 glass was researched. A thermodynamic model of K9 glass irradiated by ultraviolet pulse laser was established using the finite element software ANSYS. The article analyzed some key problems in simulation process of ultraviolet pulse laser damage of K9 glass based on ANSYS from the finite element models foundation, meshing, loading of pulse laser, setting initial conditions and boundary conditions and setting the thermal physical parameters of material. The finite element method (FEM) model was established and a numerical analysis was performed to calculate temperature field in K9 glass irradiated by ultraviolet pulse laser. The simulation results showed that the temperature of irradiation area exceeded the melting point of K9 glass, while the incident laser energy was low. The thermal damage dominated in the damage mechanism of K9 glass, the melting phenomenon should be much more distinct.