This PDF file contains the front matter associated with SPIE Proceedings Volume 8904, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

To realize the room-temperature ferromagnetism (RTFM) in diluted magnetic semiconductors (DMS), we prepared a series of Cobalt-doped ZnO thin films using pulsed laser deposition (PLD) at deposition temperatures 500°C under oxygen pressure from 2.5×10^-4 Pa to 15 Pa. To elucidate the physical origin of RTFM, Co 2p spectra of cobalt-doped ZnO thin films was measured by X-ray photoelectron spectroscopy (XPS). The magnetic properties of films were measured by an alternating gradient magnetometer (AGM), and the electrical properties were detected by a Hall Effect instrument using the Van der Pauw method. XPS analysis shows that the Co²⁺ exists and Co clusters and elemental content change greatly in samples under various deposition oxygen pressures. Not only the valence state and elemental content but also the electrical and magnetic properties were changed. In the case of oxygen pressure 10 Pa, an improvement of saturation magnetic moment about one order of magnitude over other oxygen pressure experiments, and the film exhibits ferromagnetism with a curie temperature above room temperature. It was found that the value of carrier concentration in the Co-doped ZnO film under oxygen pressure 10Pa increases about one order of magnitude than the values of other samples under different oxygen pressure. Combining XPS with AGM measurements, we found that the ferromagnetic signals in cobalt-doped ZnO thin film deposited at 500 °C under oxygen pressure 10 Pa only appear with the detectable Co²⁺ spectra from incompletely oxidized Co metal or Co cluster. So oxygen pressure 10 Pa can be thought the best condition to obtain room-temperature dilute magnetic semiconductor about cobalt-doped ZnO thin films.

Experimental performance of one-dimensional (1D) smoothing by spectral dispersion (SSD) combined with distributed phase plate (DPP) on the ninth beam of SG-II is presented. Without the application of SSD, normalized focal-spot non-uniformity of an 85% energy concentration is about 60%. Then, spectral bandwidth of the 3-ns, 1053-nm laser pulse is broadened to 0.3 nm (as 270GHz in 3ω) by a 3-GHz modulator and a 10-GHz modulator integrated in the front-end system. Spectral dispersion of 236 μrad/Å is achieved by a Littrow-configuration, 1480-l/mm grating placed between the Φ40mm faraday isolator and the third Φ40mm rod-amplifier. By using such SSD, normalized non-uniformity with the same energy concentration is decreased to 16%. A scheme of spatial power spectral density (PSD) in different directions is adopted to analyze the intensity distribution of the far-field irradiation. Based on the spatial PSD analysis, theoretical predictions of spectral peak caused by SSD’s color cycles is in excellent agreement with the experimental result. With double-frequency modulation, the amplitude of the spectral peak is reduced by ~10dB. The temporal waveform of the 1ω laser is measured. Waveform distortion criterion defining the frequency modulation to amplitude modulation conversion (FM-to-AM) is about 6% with 1ω laser energy of ~1.8kJ.

In high-power laser facilities for inertial confinement fusion, there are many large-diameter optical elements, which inevitably have some flaws on the surface. The beam is modulated by these flaws after diffraction transmission, thereby reducing the beam quality of the system. The optical field with high modulation may cause self-focusing in fused silica and thus damage the optical components, which seriously affects the load capacity of the device. Therefore, for high-power laser systems, near field beam quality also has a high demand. In this paper, the effect of flaws and nonideal wavefront of sinusoidal modulation on the near-field quality at specific position behind the focusing lens is analyzed for final target system of high power laser device based on the Huygens-Fresnel diffraction theory. Firstly the beam modulation of ideal wavefront disturbed by flaws is investigated. And the modulation by phase type flaw is more serious than amplitude type. Secondly, near field beam modulation of nonideal wavefront of sinusoidal phase disturbed by flaws is analyzed. Results demonstrate that under some specific conditions of sinusoidal phase, modulation degree is reduced and the beam quality is improved by the nonideal wavefront compared to the ideal wavefront. The results could give some references to the improvement of near field beam quality and mitigation of risk of optical damage caused by self-focusing.

The interaction between polymer of Delrin with nano-second pulse laser is investigated in laser plasma micro-propulsion. The coupling coefficient and specific impulse are measured respectively. The coupling coefficient about 42 dyne/W and specific impulse up to 646 s have been obtained. Moreover, the surface images after ablation have been observed. It is found that Delrin has less debris on ablation surface. This indicates that Delrin is a potential polymer material in laser plasma propulsion.

Caliber mortar projectiles and bombs are now tend to use the laser fuze because of its high accuracy in distance measurement，the strong ability to resist electromagnetic interference, the high angular resolution and the good concealment. Otherwise, the microlaser can bring about some alluring benefits. For instance, it can generate high quality laser beam, which has small divergence angle and high power. So, This paper summarizes some key factors which have impacts on the output of LD-pumped passively Q-switched subnanosecond microlasers, including the initial transmission of the absorber, the reflection of output coupler, the length of the cavity and the radius of the pumping laser beam, and gives the conclusion of the simulation based on the variation of the density of the reversal particle in the resonant cavity derived from the oscillation equation of the LD-pumped passively Q-switched Cr4+:YAG/ Nd:YAG laser, which provides the basis for the design of the passive Q-switched micro lasers which have high power, high repetition frequency and narrow pulse width.

Diode pumped solid state 532 nm green laser is widely required for many industrial, medical and scientific applications. Among most of these applications, high power quasi-continuous-wave (QCW) green laser output is demanded. This can be efficiently achieved through a diode-side-pumped acoustic-optic Q-switched Nd:YAG laser with an intracavity second harmonic generation (SHG). In our experiment, LBO crystal is used for the second harmonic generation of high-average-power lasers of near infrared (NIR) range, though its effective NLO coefficient d_eff is relatively small. It is because of its high damage threshold (greater than 2.5 GW/cm²), large acceptance angle, small walk-off angle, and the nonhygroscopic characteristic. In this paper, we reported a high-repetition-rate high-power diode-side-pumped AO Q-switched Nd:YAG 532 nm laser. A plane-plane cavity with two rods, two AO Q-switches and the type II critical phase-matched LBO at room temperature were employed. Under the LD pump power of 480 W, 95.86 W at 1064 nm wavelength was achieved when the repetition rate was 15 kHz, and the 532 nm average output power of 44.77 W was obtained, with a pulse width of 111.7 ns, corresponding to an optical to optical conversion efficiency of 46.7% from 1064 nm to 532 nm. The 532 nm average output power was 40.10 W at a repetition rate of 10 kHz with a pulse width of 78.65 ns. The output characteristics of the SHG varying with the pumping current and the pulse repetition frequency (PRF) of the laser were also investigated. Further improvement of the SHG is under study.

Long pulse laser starts to have a prominent role in many applications. So, How to design and calculate the parameters of the high power long-pulse solid-state laser is illustrated, experimentally and arithmetically. How to design a pumping chamber is illustrated, with a double-ellipse cavity. Optical resonator losses are got experimentally in details. Efficiency factor and system slope efficiency are calculated experimentally. Illustration for how to get the optimum mirror reflectivity is mentioned. Beam waist and beam divergence also studied experimentally. The designed system has 10J output energy with pulse width 20msec for efficiency factor 1.1% and a combined loss 0.181 inside resonator. Average system efficiency, gain coefficient and fluorescence power for four different output mirror reflectivity are 0.328%, 0.00994cm^-1 and 144.92W respectively. 6KW/cm² power density inside resonator is obtained which corresponds to 585W maximum output power. An optimum mirror reflectivity 57% is for 208.2KW input power. The beam waist and beam divergence are recorded to be 0.66cm and 8.86mrad. Calculations show that, 11.7J output energy can be obtained by more optimization based on the designed system.

The gain and refractive index combination guiding is investigated by simulating a dual-end pumped rod Nd:YVO₄ amplifier. From the simulation, it is indicated that the large transverse gain gradient and the gain coefficient are contribute to the gain guiding to enhance the beam quality. The appropriate spherical aberration in the input beam is helpful for improving the beam quality of output beam. Moreover, the gain saturation determines which one could dramatically influence beam quality between the gain guiding and the refractive index guiding.

Laser has several advantages, such as strong anti-interference ability, quick speed, high power, agility and precision. It is widely applied in military and medicine fields. When laser acts on human body, biological tissue of human body will appear the phenomenon of ablation and carbonization and solidification. In order to effectively defend excess damage by laser, the thermal effect research of skin tissue should be carried out. The heating rate and thermal damage area should be studied. In the paper, thermal energy production and thermal exchange loss used in living tissue is analyzed. The rule of thermal transfer that is irradiated by high power laser is discussed. The model of two dimensional skin tissues is built. The two dimensional transient temperature distribution generated by laser irradiation in bio-tissue is numerical simulated using finite element method. The temperature change trend generated by pulse laser and continuum laser in different radial length and axial depth bio-tissue are studied respectively. The results show that FEM method can reflect the photothermal conversion of bio-tissue exactly. Temperature is the highest in the local tissue by laser irradiated directly. The highest temperature decreases along with increasing radial length and axial depth. The highest temperature rise generated by pulse laser is more than continuum laser’s. The highest temperature generated by pulse laser is not monotone increasing but is oscillation trend. The highest temperature generated by continuum laser is monotone increasing. The temperature rise mainly occurs in exodermis and derma. The temperature rise is not very significant in fat acid lining.

The atmospheric transmittance of high power laser along a ground-space slant path has been comprehensively investigated in this paper, which could be used for performance prediction and parameter estimation in the field of laser engineering. First of all, the atmospheric transmittances along a ground-space slant path are studied with the different launch parameters of high power laser. The center wavelength of laser is a critical element that affects the atmospheric transmittance, while the influences of other parameters can be almost negligible. The atmospheric transmittances of high power laser along a ground-space slant path are secondly researched under the different meteorological conditions. The atmospheric transmittances of high power laser along a ground-space slant path are lastly calculated under the different propagation conditions. The results indicate that atmospheric transmittance through the whole atmosphere decreases as the zenith angle increase; the differences remain in 2 percent when the zenith angle is less than 20 degree for 532nm laser. In the view of propagation length, it is the range below the altitude of 6km that mainly affects the transmittance of high power laser along a ground-space slant path.

We derive and calculate numerically laser linewidth by means of the laser rate equation in an extending diode laser cavity provided by an end reflector. We found that narrow linewidth is closely connected with phase modulation and frequency modulation. The numerical simulation shows the dominance of effect over another depends on inherent factors such as the α coefficient, bandwidth of laser, length of external cavity, reflective coefficient etc.

Power scaling and beam divergence compression of 980 nm bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) are presented in this paper. First, the relationships among the reflectivity of the n-doped distributed Bragg reflector, threshold current, and output power were analyzed, and the n-DBR reflectivity was optimized to achieve higher slope efficiency in a relatively low threshold current. Second, the influence of the p-contact on the current density distribution inside the active region was analyzed using the three-dimensional finite-element method. Uniform current distribution was achieved by optimizing the diameter of the p-contact, and a consequent improvement in beam divergence was observed. A low divergence of 5.4° was obtained for a single device with continuous-wave (CW) of 1.46 W at room temperature. The 8×8 VCSEL array showed a divergence angle of 10.2° at 4A. This array afforded a CW output power of 1.95 W under an injected current of 4 A and a pulse output power of 115 W under a pulse drive current of 130 A, a pulse width of 100 ns, and a repetition frequency of 100 Hz. VCSEL array chips were packaged in series to form a “quasi-array” to further increase the output power. This series achieved a peak output power of 475 W under a pulse drive current of 120 A.

High peak power picosecond laser ablation of silicon draws great attention in solar cell manufacture,laser optoelectric countermeasure applications, eta. This paper reports the damage process of ultrafast lasers interaction with silicon,which is based on Two-Temperature Model(TTM) and 1-on-1 damage threshold test method. Pulsed laser caused damage manifests in several ways, such as heat damage, mechanical effect and even eletrical effect. In this paper, a modified Two Temperature Model is applied in ultrashort laser interaction with silicon.The traditional Two-Temperature Model methods is proposed by Anismov in 1970s to calculate the interaction between ultrafast laser with metals, which is composed of free electrons and lattice. Beyond the carrier and lattice temperture model, an additional excited term and Auger recombination term of carriers is taken into account in this modified Two-Temperature Model model to reflect the characteristics in semicondutors. Under the same pulse-duration condition, the damage threshold is found to be 161 mJ/cm² and a characteritic double-peak shape shows up. As the pulse energy density rises from 50mJ/cm² to 161 mJ/cm², the difference between carrier and lattice temperature steps down proportionally.Also,a detailed interaction process between photon-electron and electron-phonon is discussed. Electron and lattice temperature evolutes distinctly different, while the former is much higher than the latter until heat tranfer finished at 200 picoseconds. Two-peak feature of electron temperature is also identified. As the pulse duration increases from 20 picosecond to 60 picosecond, the he difference between carrier and lattice temperature steps down significantly. The calculated damage threshold does not change fundamentally, remaining approximately 0.16J/cm². Also, the damage mechanism is found to be thermal heating with the pulse width between 20 and 60 picoseconds at threshold fluences which is identical to experiment test result. This research is valuable to laser applications and/or laser shielding applications.

Criteria of selecting the slab size in high-power end-pumped Nd:YAG zigzag amplifier were given, the optimized slab thickness is suggested 2~3 mm, with the corresponding slab length less than 15 cm. Power extraction in the slab was calculated by a smart ray tracing technique, the optimized input flux is 3~4 times the saturated flux (Is) with a maximum optical-optical (o-o) efficiency of 44.5% for the single-slab single-pass stage, and 0.1~0.2 Is with a maximum o-o efficiency of 41% for the four-slab angularly double-pass stage.

A compact transversely excited atmospheric (TEA) CO₂ laser with high repetition-rate was reported. The size of the laser is 380 mm×300 mm×200 mm, and the discharge volume is 12×10³ mm³. The laser cavity has a length of 320mm and consists of a totally reflective concave mirror with a radius of curvature of 4 m (Cu metal substrate coated with Au) and a partially reflecting mirror. The ultraviolet preionization makes the discharge even and stable，the output energy can be as high as 28 mJ under the circumstance of free oscillation, and the width of the light pulse is 60ns．To acquire the high wind velocity, a turbocharger is used in the system of the fast-gas flow cycle. When the wind speed is 100m/s, the repetition rate of the transversely excited atmospheric CO₂ laser is up to 2 kHz. On this basis, a dual modular structure with two sets of the gas discharge unit is adopted to obtain a higher pulse repetition frequency output. The dual discharge unit composed two sets of electrodes and two sets of turbo fan. Alternate trigger technology is used to make the two sets of discharge module work in turn with repetition frequency of 2 kHz, the discharge interval of two sets of the gas discharge unit can be adjusted continuously from 20 microseconds to 250 microseconds. Under the conditions of maintaining the other parameters constant, the repetition frequency of the laser pulse is up to 4 kHz. The total size of laser with dual modular structure is 380mm×520mm×200mm, and the discharge volume is 24×10³ mm³ with the cavity length of 520mm.

Pre-amplifier between the frontend and main power amplifier is the key unit of high power laser divers. The recent progresses on the off-axis quadruple pass amplifier are presented, which include the beam path design, parasitic oscillation research and experimental results. A single longitudinal mode, temporally shaped laser pulse with 5ns pulse duration at 1053nm is injected into a Nd: Glass regenerative amplifier, which can provide a 12mJ energy output with 0.5% long term energy stability. The quadruple pass amplifier is designed as an off-axis pattern. With 1.3mJ energy injection, amplified pulse with 16.5J can be achieved, and the measured output energy stability of the amplifier is 7.3% (PV) at this output energy level, corresponding to a 21 shot result. The total gain of the amplifier is more than 10,000. The parasitic oscillation was analyzed and discussed, and the parasitic mode and pencil beam are neither observed in the experiment.

Laser plasma drag reduction is a new method to reduce the wave drag of hypersonic flight. The research of the laser plasma drag reduction performance is an important work. The purpose of this paper is investigating laser plasma drag reduction by numerical simulation to enhance the understanding of the drag reduction mechanism, get the drag reduction performance in different conditions, and provide references for laser plasma drag reduction experiment in the future. Based on summarizing correlative references systematically, through building the model of energy deposition and comparison the simulated results to the empirical formula and computation results to verify the program correctness, the influence of laser energy parameters to laser plasma drag reduction were simulated numerically for optimize the performance. The follow conclusions were got by numerical simulation: The computation program can well simulate the interacting of LSDW(laser supported detonation wave) to the bow shock in front of the blunt body. Results indicate that the blunt body drag could be decreased by injecting laser energy into the incoming hypersonic flow. The correctness of program was verified by compare result to the experiment and computation results. Blunt body drag will be greatly decreased with injected laser power increased, The bigger laser power is injected, the more drag decreases. There’s an energy saturation value for each laser power level, the injecting laser power effectiveness values are never quite high for all laser power level. There is an optimized energy deposition location in upstream flow, this location is right ahead of the blunt body. When the distance from deposition location to the surface of blunt body is 5 times the blunt radius, blunt body drag decreased the most. This paper investigated the parameters which primary influence the performance of drag reduction. The numerical simulation data and obtained results are meaningful for laser plasma drag reduction experiment investigation. Aerodynamic drag, laser plasma, hypersonic, drag reduction, numerical simulation

As an intrinsically surface-specific technique, Second Harmonic Generation (SHG) is widely used in the study of interface in recent years. The SHG signals from the air/liquid interface of Rhodamine B and Sodium Dodecyl Benzene Sulfonate (SDBS) aqueous solutions were obtained and analyzed, which demonstrate that the SHG signal intensity of Rhodamine B is stronger than that of SDBS. Compared with one single solution, the SHG signal intensity of the mixed aqueous solution of Rhodamine B and SDBS decreases. From the UV-VIS absorption spectrum of the two aqueous solutions, it can be seen that Rhodamine B has an absorption peak closer to the second harmonic frequency. Therefore the resonance of the second harmonic frequency with the frequency of the dipole transitions of the chromophore considerably enhances the signal intensity. Furthermore, the hyperpolarizabilities of the molecules of Rhodamine B and SDBS are calculated from first-principles, which reveal that the hyperpolarizability of Rhodamine B molecule is greater than that of SDBS molecule. When they are mixed, molecules of Rhodamine B and SDBS gather together because Rhadamine B molecule carries positive surface charge and SDBS is anionic surfactant, causing the decrease of the SHG intensity of the mixed solution.

In order to study deeply damage mechanism of HgCdTe crystal irradiated by multi-pulsed CO₂ laser and obtain the characteristics of surface morphological and chemical composition changes. Firstly, Irradiation effect experiment is conducted on the Hg_0.826Cd_0.174Te crystal by pulsed CO₂ laser, which has a pulse width of 200ns and repetition frequency ranges from 1 Hz to 100 kHz. Then morphological and chemical composition changes of Hg_0.826Cd_0.174Te crystal is measured by field emission scanning electron microscope (FESEM) and damage threshold is obtained by morphology method. Finally, the impact of laser power density on morphological and chemical composition changes is analyzed. The research results show that: damage threshold of Hg_0.826Cd_0.174Te crystal which is irradiated by multi-pulsed CO₂ laser is 950 W/cm². The crystal surface melting phenomenon is very obvious, the obvious crack which is caused by thermal stress is not found in the surface, and a large number of bulges and pits are taken shape in the laser ablation zone. Chemical composition changes of the crystal are obvious, and a lot of O element is found in the laser ablation zone. With the increase of laser irradiation power, the content of Hg element decrease rapidly, the content of Cd, Te and O element raise by degrees, and chemical composition changes of the crystal are more and more obvious. When the irradiation power density is 1.8kW/cm², the surface becomes smooth in the ablation zone due to the impact of laser impulse force, and the content of the chemical compositions is that Hg accounts for 0.23%, Cd accounts for 21.38%, Te accounts for 26.27%, and O accounts for 52.12%. The conclusions of the study have a reference value for the Hg_0.826Cd_0.174Tecrystal in the application of making infrared detector and pulsed CO₂ laser in the aspect of laser processing.

In this paper, we study and establish the theoretical model of thermal stress damage of dielectric film in film/substrate systems caused by long-pulse laser, based on which transient distributions of temperature field and thermal stress field are simulated using the finite element method(FEM) and then analyze the mechanism of the damage. In accordance with the basic equation of heat conduction equation and thermal stress equation, the physical model of dielectric film and the substrate transient temperature field and thermal stress field is developed with the assumption that the dielectric film and the substrate are isotropic and their thermal parameters do not change with temperature. On the foundation of theoretical analysis, transient of temperature field in dielectric film in film/substrate systems under long-pulse laser irradiation is simulated and calculated. The numerical results indicate that great temperature gradient exists in dielectric film and substrate in radial direction but smaller one exists in axial direction. When the laser power density is increasingly larger, the temperature gradient in radial direction is larger and the temperature in the center of the film is higher. Transient thermal stress field in dielectric film in film/substrate systems under long-pulse laser irradiation is simulated. Numerical results show that, the damage to the dielectric film caused by long-pulse laser is mainly due to thermal stress damage process which circumferential stress acts a primary role in. Such damage is a final result of the substrate being under thermal stress. For film/substrate system, the damage under long-pulse laser radiation starts from the substrate. When the laser power density is increasingly larger, the dielectric film is more vulnerable to damage and damage zone is greater. The result of this paper provides theoretical foundation not only for research of theories of dielectric film and substrate thermal stress damage and its numerical simulation under laser radiation but also for long-pulse laser technology and widening its application scope.

A model of coupled dynamics for supersonic airbreathing propulsion is developed to simulate the development process of the thruster’s flowfield. The influence of the inflow speed, from 1 to 4 Mach, on the laser propulsion performance is investigated numerically. The results indicate that the inflow speed has a marked effect on the propulsion efficiency. Under the same laser parameters, the larger inflow speed leads to lower thruster and impulse coupling coefficient. By analyzing the phenomena in the complex unsteady flowfield, we found that the bow shock occurring out of the surface of the thruster due to supersonic inflow is the real cause of the performance worsening and air drag reduction becomes a very important task at supersonic laser propulsion.

The method for generating temporal flat-top waveform and spatial flat-top profile femtosecond pulse beam by phase and polarization controlling is proposed and demonstrated. Based on direct wave front phase modulating, flat-top spatial intensity distribution can be obtained. Combining a folded 4f zero-dispersion system with a polarization controlling setup, the temporal flat-top waveform is generated. Experimental results indicate that for the input both temporal and spatial Gaussian pulse beam with 363 fs temporal width and 1.5 mm beam waist, the temporal width of the output shaped pulse beam is 1.2 ps and 1.9mm beam waist, and the rms variation is about 9.2%, which prove that the temporal flat-top and spatial flat-top femtosecond pulse beam can be generated effectively.

Based on the real-time adaptive femtosecond pulse shaping system, the phase compensating algorithms which can effectively compensate the output shaping waveform distortions are investigated in detail. The simulated-annealing algorithm that can modify the output pulse temporal waveforms iteratively toward the target shapes using the second harmonic generating frequency resolved optical gating (SHG-FROG) measurement as feedback is proposed. Compared with the cross-correlation feedback measurement method, the output based on the SHG-FROG measurement method is better and the temporal chirp of the output pulse is compensated more effectively. Moreover the performance of the SHG-FROG measurement feedback algorithm is compared to other exemplary standard approaches such as the Genetic Algorithm based on the cross-correlation feedback measurement method, the result is much better.

A generation spectrum of a high-power Yb-doped fiber amplifier (YDFA) becomes broader with increasing power in the master oscillator power amplifier (MOPA) configuration, which degenerating the coherence of the laser. In this work, a spectral model had been proposed for the high-power YDFA in Continuous Wave (CW) region. A fiber amplifier was built at the 600W level and experiments were conducted for its output spectral characteristics based on this model. Through this model, the output spectrum of high-power YDFA in CW region could be calculated. Though the theoretical spectra were in little different from the measured ones, the predictions of the theory were still in excellent quantitative agreement with the experimental results.

The physical limit for the maximum extractable power of Tm-doped silica fiber lasers in resonantly-pumped configuration is analyzed. The effect of thermal fracture, thermal lens, melting of the core, optical damage, finite pump brightness and the nonlinear effects (stimulated Brillouin scattering or stimulated Raman scattering) are taken into consideration. According to the numerical simulation, a maximum extractable power of 56.6 kW and 2.11 kW could be achieved by theTm-doped fiber sources in resonantly-pumped configuration for the broad bandwidth and single-frequency case, respectively. Strictly single-mode of these cases are also taken into consideration, and the maximum extractable powers are 12 kW and 1.25 kW. The physical limit mechanism derived by this method proves that the Tm-doped fiber sources in resonantly-pumped regime has a significant advantage over that in diode directly-pumped regime, thus having practical significance for increasing the output power.

In this paper, we propose an optimized design of the picosecond MOPA fiber laser by using hybrid-doped Yb fibers. The detailed implementation is that high-doped gain fiber with relatively small fiber core is adopted in the low-power pre-amplifiers, thus the shortest fiber could be ensured and the thermal load is not so heavy. In the power amplifier stage, the normal-doped large mode area gain fiber is utilized, then the thermal effects can be minimized and the output beam quality could be ensured. The design simultaneously takes into consider the output beam quality, thermal load, nonlinear phase shift, pulse peak power of the picosecond fiber laser. With using the existed Yb-doped fibers, we demonstrate a high-power picosecond MOPA fiber laser with the proposed method. The average output power is up to 110 W, the total optical conversion efficiency is 63.2%. No stimulated Raman scattering, amplified spontaneous emission and residual pump light are observed in the output spectrum. The - 6 dB bandwidth of the output spectrum at the full output power is ~ 4 nm.

Interference mechanism of laser disturbing infrared detector is analyzed. The disturbing grade was separated into four levels according to interference effect. The levels are saturation, melting, vaporization and plasma. The responsivity of a detector will drop and it can’t work effectively when it was saturated. Its performance wills recovery when the interference disappeared. Melting, Vaporization and plasma will lead to permanent damage. The main damage to detector is thermal damage for induced laser. The reason is that the detector will melt or evaporate when it absorbed the energy of induced laser. For HgCdTe detector, the damage appeared as Hg precipitation. It appeared as In exfoliated from welding outlet line of HgCdTe crystal or HgCdTe melting when the temperature of detector is higher. Since Vanadium Oxide has reversible transformation characteristic between semi-conductor, metal and insulator, it can be used to protect detector from laser damage. Vanadium Oxide can be made as thin film coatings on optical system to protect the detector. the phase transformation point temperature of VO₂ is 68°C,a few doping method can decrease the transformation temperature. These mean that less energy can make VO₂ film’s temperature increase to transformation point. VO₂ film protecting HgCdTe detector was used as an example to estimate the protection effect. For an HgCdTe detector, its responsivity will drop two orders of magnitude when its temperature raises 70K. This case be regard as that the detector was disturbed. When a CO₂ pulsed laser beam with 0.1μ s∼10μs pulse width was incidence an HgCdTe detector, its heat conduction depth is 0.32∼3.2μm and its thermal diffusion can be ignored. The damage energy density threshold value is E_in=1.55J/cm². When CO₂ pulsed laser beam incidence the detector through certain thickness VO₂ film, the VO₂ film will has transformed from semiconductor state to metallic state before the laser beam damage the detector. The energy of the laser beam will be total reflected. VO₂ can be used as an intelligent preventer to protect detector against laser.

Photonic crystal fiber has been widely used in visible and near-infrared supercontinuum generation due to its flexible dispersion control and high nonlinearity. However, the maximum average output power of supercontinuum from a photonic crystal fiber has not exceed one hundred watt owing to the small core diameter of the photonic crystal fiber and the low coupling efficiency between the pump and the photonic crystal fiber. Recently, supercontinuum generation directly from a nonlinear fiber amplifier attracts lots of attention as a result of its simple structure and low splicing loss and many excellent results have been achieved either in low and high average power, which is proved to be a promising method to realize kilowatt level high power near-infrared supercontinuum. However, the numerical study on high power near-infrared supercontinuum generation from a nonlinear fiber amplifier has been rarely reported, so there is great necessity to carry out some theoretical study on it. In this paper the complex Ginzburg-Landau equation is used to describe the formation and propagation of high power near-infrared supercontinuum generation in a nonlinear fiber amplifier. The chromatic dispersion of the ytterbium-doped fiber is measured by a Mach-Zehnder interferometer. The roles of the small signal gain, input pulse width and initial chirp of the input pulse played on the continuum formation are analyzed in detail. The results are in good agreement with the experiments which can provide some theoretical guidance on future optimization of the flatness and width of the supercontinuum generation from a nonlinear fiber amplifier.

The smile effect is caused by the thermal stress in the packaging process. If packaging technology of a diode laser array is poor, smile effect will be very bad and the smile effect will vary with storage time. To accurately measure smile effect and to objectively compare the different measuring methods for smile effect, a set of optical system is designed for measuring the smile effect. By using an image amplification method, the smile effect of a diode laser array is accurately measured, and the measurement error is about ±0.1μm. By researching, the heat sink surface flatness has little influence on smile effect. However the solder quality is a critical factor for smile effect. That is to say, there is more voids, the corresponding smile effect is more serious in this area. Reflow soldering curve has a major impact on smile effect in the packaging process of a diode laser array .During reflow soldering process, accelerated cooling before solidification and slow cooling after solidification not only can commendably reduce voids and smile effect ,but also can effectively solve the smile effect with storage time variation problem .By optimizing the reflow soldering curve of a diode laser array , the smile effect has been controlled within ±0.5μm..As the smile effect values of a semiconductor laser array is diminished and the beam quality of a laser diode array is improved significantly. The recommended method provides favorable conditions for the beam collimation and shaping of a semiconductor laser array.

Based on the phase modulation characteristics of optically addressed liquid crystal spatial light modulator (OA-LC-SLM) which is realized by controlling the power of addressing light, a physical model of coherent beam combination fiber laser using a bunch of fibers and a device of OA-LC-SLM is established on the theory of diffraction optics and liquid crystal birefringence effect. On the basis of this model, the properties of given scheme of coherent beam combination fiber laser are investigated including main lobe distribution and ability of phase modulation. Meanwhile, the plot functions of phase modulation versus the optical power of addressing light are obtained on different given driving voltage conditions and fiber alignment parameters such as core diameter and filling factor. After the numerical simulation, it shows that, this coherent beam combination fiber laser using OA-LC-SLM demonstrates an ability of coherent beam combination on the far field. With the increase of core diameter, the combination efficiency is improved better, and the divergence angle decreases narrower.

As currently, laser calibration, laser radar, laser ranging and the relative field raised up the demand for high magnification laser beam expander. This article intends to introduce a high-energy laser beam expander research and design, large- diameter, wide-band, high-magnification and small obscuration ratio are the main features. By using Cassegrain reflective optical system, this laser beam expander achieves 24 times beam expand, and outgoing effective limiting aperture is Φ600 mm, band scope between 0.45μm to 5μm, single-pulse laser damage threshold greater than 1J/cm², continuous-wave laser damage threshold greater than 200W/cm² and obscuration ratio 1:10. Primary mirror underside support uses 9 points float supporting, lateral support mainly depends on mercury belt support and assists by mandrel ball head positioning support. An analyzing base on finite element analysis software ANSYS, and primary mirror deformation status analysis with debug mode and operativemode, when inputs four groups of Angle 170°, 180°, 210° and 240° , mercury belt under each group of angle load-bearing is 65%, 75% , 85% and 100% respectively, totally 16 workingcondition analyze results. At last, the best way to support primary mirror is finalized. Through design of secondary mirror to achieve a five-dimensional precision fine-tune. By assembling and debugging laser beam expander, Zygo interferometer detection system proof image quality (RMS) is 0.043λ (λ=632.8nm), stability (RMS) is 0.007λ (λ=632.8nm), and effective transmission hit 94%, meets the requirements of practical application completely.

Coherent combination of multiple laser amplifier is an important technique for high power and high beam quality laser. Laser amplifier uses master oscillator power amplifier (MOPA) configuration for narrow bandwidth and high beam quality laser. Then active phase control is used to make multiple laser amplifier phase synchronization for coherent spot in the far field. The center spot is N times brighter than the one of incoherent combination. At present, researchers have used this method to achieve 1.56kW coherent combination of nine fiber lasers and 105kW of seven slab lasers. The phase noise of the laser amplifier is an important factor affecting the coherent combination. There are two key technologies in the coherent combination. The one is fill factor of multiple laser spatial distribution, which determines main lobe energy of coherent spot. And the other is the phase noise of the laser amplifier, which decides stability of the coherent combination. The phase noise of laser amplifier is caused by many factors, mainly thermal disturbance and mechanical vibration. Due to the complexity of the phase noise generation, the research on phase noise is generally concentrated in the qualitative analysis. The phase noise is generally considered the time phase noise. It is phase dithering from variation refractive index by external disturbance. A variety of factors, such as temperature changes, mechanical vibrations, the pump power, affect phase noise. We establish an externally imposed discrete disturbance source on fiber laser amplifier and then analyze above-mentioned factors independently and quantitatively by the method. The experiments demonstrate space phase noise, dithering of beam direction, is simultaneously induced by either mechanical vibration or thermal disturbance. This experiment is significant for understanding mechanism of the phase noise and suppression of phase noise.

We report on the mid-infrared supercontinuum laser output using a short piece of single-cladding Tm-Ho co-doped fiber, pumped by a 1565 nm pulsed laser. The seed laser was amplified using a two-stage Er-doped master oscillation power amplifier (MOPA). The seed laser was amplified to 260.8 mW with repetition rate of 100 kHz. The amplified 1565 nm pulse laser passed through a piece of 500 m long single-mode 9/125 G652D communication fiber, then the laser was injected into a 2 m long 9/125 Tm-Ho co-doped fiber. The laser had output power of ~ 20 mW, and the laser’s spectrum was measured by an optical spectrum analyser (YOKOGAWA). By changing the 1565 nm seed laser’s repetition rate and pulse duration, mid-infrared supercontinuum was generated. The energy levels of Tm³⁺ and Ho³⁺ icons acted with the different wavelength of the pulse laser, then flat and broadband mid-infrared supercontinuum between 1800 nm ~ 2200 nm was generated. The output power can be scaled up by increasing the 1565 nm laser’s power directly. This supercontinuum generated by single-cladding Tm-Ho co-doped fiber may provide meaningful reference for mid-infrared supercontinuum generation using other rare-dearth-doped fibers.

For the thermal blooming of the beam path indoor, solving the coupling equations of optical field and fluid field completely is a meaningful and important subject. In this paper a numerical emulation platform for solving the coupling equations was established. The laser beam coupled with the fluid field by the method of User Defined Function which was offered by the CFD software. Thermal blooming effects in the beam path indoor of the line pipe are modeled by the established numerical emulation platform. In order to testify the rightness of the numerical emulation results, steady-state thermal blooming effects in the axial pipe flow are calculated by the theoretical methods, and corresponding experiments are also carried out. The results indicate that the numerical emulation platform is creditable in simulating the thermal blooming of axial pipe flow.

The nonlinear refractive response of a copper phthalocyanine film fabricated by the electro-deposition is investigated by a modified top-hat Z-scan with 19 picoseconds pulse at wavelength of 532 nm. Compared to the top-hat Z-scan, the curve of modified top-hat Z-scan for the nonlinear refraction shows a single peak rather than a peek-valley curve. Furthermore, the sensitivity of this new technique can be more than two orders of magnitude enhanced. The results show that the film has obvious response of nonlinear refraction. The theoretical simulation fit well with experimental results.

Based on the actual working environment of pulse LD dual-end pumped Tm:YAG crystal, time-dependent temperature field analytical expression and the time-varying thermal focal length are deduced by the integral transform method. Additionally, the effects of pump power, repetition frequency and duty ratio on axial transient temperature distribution and time-varying thermal focal length of pulse LD dual-end pumped Tm:YAG rod are simulated and analyzed. The results show that the temperature distribution reaches steady state respectively by 11, 14, 15 pulses under pump power of 30W, 35W and 40W, respectively, while the frequency is 100Hz and the duty ratio is 50%. Under the condition mentioned above, the temperature of the crystal rod on both ends of the center arrives 34.7°C, 37.5°C, 40.3°C, which is 1.8°C, 2.1°C, 2.4°C higher than the center of rod. And the thermal focal length is in the range of 31.5-41.5cm, 26.5-34.6cm, 22.9-29.7cm, respectively. When pump energy is 100mJ, frequency at 110Hz, 120 Hz, 130Hz and duty ratio at 55%, 60%, 65%, respectively, the temperature distribution reaches steady state respectively by 13, 15, 16 pulses, and the temperature of the rod on both ends of the center respectively arrives 30.0°C, 30.9°C, 31.8°C, which is 1.3°C, 1.4°C, 1.5°C higher than the center of rod, and thermal focal length is in the range 46.4-58.8cm, 42.7-51.6cm, 39.5-45.9cm, respectively. Namely, as the increase of the pulses number, the distribution of the temperature and the thermal focal length in crystal rod appear jagged and eventually get to the periodic distributions. With the increase of the pump power, repetition frequency and duty ratio, the temperature difference between the crystal rod on both ends of the center and the center of rod is increasing, while time-varying thermal focal length gradually becomes shorter and the fluctuation range is smaller until it reaches steady state. The results provide theoretical basis for heating compensation and cavity design of pulsed thulium doped lasers.

266nm UV laser has a wide range of applications in various fields by its advantages in high single photon energy and high resolution, which also has a development gradually moving in the direction of high power and high conversion efficiency. In the process of high-power laser frequency doubling, BBO crystal inevitably absorbs part of fundamental light power and frequency doubled light power, it induced the temperature rise along the direction of radiation in crystal and destroyed the phase-matching conditions of BBO crystal that lead to phase mismatching. In order to improve harmonic conversion efficiency as well as reduce the influence of output power and beam quality caused by phase mismatching, in this paper we analyzed the process of phase mismatching, established the thermal-induced phase mismatching model by using analytical expression of the nonlinear crystal temperature field equation which has been given, and the three-dimensional phase mismatching distribution were obtained. There are three major contributions in the paper. Firstly, the working process of the nonlinear crystal was analyzed, and the physical and mathematical models of temperature distributions were established, and the BBO crystal three-dimensional temperature distributions were also obtained. Secondly, a variety of factors that affect the temperature distributions within the BBO crystal were summarized. For different 532nm waist radius and 532nm input power, they were numerical simulated use of MATLAB. Finally, combined with the above analysis, the physical and mathematical models of phase mismatching caused by energy absorption of BBO in forth harmonics generation were established, the phase mismatching distributions in the crystal were simulated as well, especially the changes to phase mismatching distributions with different parameter were analyzed. Combination of the multiplier theory, the influence of phase mismatching on frequency doubling conversion efficiency was analyzed. The results indicate that the physical model which established in this paper can explain the physical reasons in high-power laser frequency doubling system very well, such as the reduce in conversion efficiency and output power and beam quality. All research results play instructive effect at the improvement of conversion efficiency and the compensation for the phase mismatching for further research.

In order to compensate the low order aberrations effectively and rapidly, a new method is developed to study the wavefront compensation of a reflective beam shaping system by using simulation experiments. The system consists of three cylinder mirrors and a spherical mirror. By inserting different Zernike phase screens, many sizes and species of low order aberrations can be simulated. Then the data communication is set up between Matlab and Zemax based on dynamic data exchange (DDE) technique. The configuration parameters of the system constructed by Zemax could be regarded as variables, and the beam shaping system as the transfer function, overall appropriate optimization algorithm was utilized to solve the optimal configuration to make the compensation system most effective.

Great progress has been made in fiber laser technology especially the high power fiber laser. One of the key techniques to acquire higher output power is coupling more pump laser into the double-cladding fiber using the fiber combiner. Fiber splices exist in both manufacture of the combiner and integration of the fiber components. The optical waveguide structure of the splice point has great effect on the insertion loss and modal content for the fiber laser system. Thus it is important to use proper method to compute the insertion loss of the splice points. This is also vital in the manufacture of fiber combiner because the structure must be precisely controlled in order to acquire low insertion loss for the signal arm of the combiner to ensure the capability of sustaining high power laser. Generally speaking, there are two common methods to compute the insertion loss of splice points: the mode field diameter (MFD) and the modal overlap integral (MOI). The MFD method is simple but its accuracy is relatively lower, while the MOI is more accurate than the MFD but also more complicated. We use both two methods to compute the insertion loss of the signal arm of a (6+1) ×1 fiber combiner. The result shows that the MFD method is appropriate when there is only fundamental mode at the splice point. At the mode field matched point, the insertion loss is 0dB when using the MFD method while 0.29dB when using the MOI method. This indicates that the MOI method is more accurate than the MFD method to predict the minimum insertion loss and the optimal structure. Meanwhile, the MOI method can explain the different insertion loss for the co-propagating situation and the counter-propagating situation for the fiber combiner which cannot be explained by the MFD method. If there are higher order modes passing through the splice point, the MFD method is also inappropriate.

We report on a LD dual-end-pumped 792nm continuous wave operation Tm:YLF laser. Firstly, the rate equation of LD end-pumped CW operation Tm:YLF laser were established, in which the energy transfer upconversion and without energy transfer upconversion under continuous-wave considerate were considered, as well the pump threshold and the slope efficiency of the laser system were analyzed. Simultaneously, the cavity stability condition and the pattern matching of the plano- concave resonator were analyzed according to ABCD Matrix theory. Comparing respectively the laser threshold and the slope efficiency and optical-optical conversion efficiency under circumstances which the output mirror transmittance of 15% and 23%. In addition, the M2 of the output laser were contrasted and analyzed in adjusting the resonator cavity length by using different radius of curvature of the output mirror in 150mm, 200mm and 300mm all in the above case. As the process of thermal lens focal length changing greater than 90mm, it exhibited that the two fundamental modes in the cavity resonator matched well in numerical simulation when the radius of curvature of the output mirror was 300mm, as well the two fundamental modes matched well when it more than 100mm in a certain pump power. We designed a single LD dual-end-pumped continuous wave operation Tm:YLF laser. Using Tm:YLF (3 at.%) crystal for gain medium, which the size was 3×3×14mm³. In experiments, the Tm:YLF laser crystal keeps 291K and the temperature control method is water cooling. The length of the resonator was 135mm when L shape plano-concave resonator was applied, and the radius of curvature output mirror was 300mm, as well as the temperature of the Tm:YLF laser crystal was 291K. The output laser we observed by this system and the central laser wavelength was 1944nm. The threshold power was 8.11W and the highest output power reaches to 4.01W when the totally input pump power was 17W, and the optical conversion efficiency was 23.6%. The far-field divergence angle was 3.8mrad after calculation. Respectively. The experimental results are coinciding with the theory.

The concept of cascading Photonic Crystal Fiber (PCF) tapers is proposed, and the numerical model of supercontinuum (SC) generation in cascaded PCF tapers is clarified. Using self-compiled program, the SC generation in cascaded PCF tapers with identical and different structural parameters are numerically simulated. Hence the function of cascading is illustrated. Via cascading PCF tapers with same structural parameter, we can overcome the limitation of the tapering rig to enhance the nonlinear interaction length. Via cascading PCF tapers with different structural parameter, we can not only enhance the interaction length, but also obtain higher nonlinearity and more manageable dispersion to increase the qualities of SC, such as spectral range and flatness.

It report a continuous wave Ho:YAG laser pumped by1.91 μm Tm Laser. It important to thesis analyzed the output characteristics of Ho laser pumped by continuous Tm laser.The rate equation of Ho laser in continuous-wave operation was put forward. The rate equation was solved to analyze the influence of upconversion effect to the output power, slope efficiency and threshold power in CW operation .The transition branching ratio between the energy levels was taken into consideration while discussing the influence of up conversion.Through the simulation analysis on the output characteristics, consider the influence of upconversion effect than to ignore the influence of upconversion effect, The threshold power increased by 0.34W, the highest output power of the reduced 2.89W, the slope efficiency was decreased by 16.1%.Respectively，For all the experiments, the Tm:YLF laser crystal keeps 292K and the temperature control method is water cooling. When we applied L shape plano concave resonator, the length of the resonator is100mm, the radius of curvature output mirror is 150mm and the temperature of theHo:YAG laser crystal is 292K, we observed the central laser wavelength is 2.09μm. The highest output power reaches 8.23W when the totally input pump power is18W. And the slope efficiency is 45.7%, respectively. The experimental results are coincide with the theory.

We have fabricated waveguides in z-cut Lithium niobate using focussed femtosecond pulses inscription of the bulk material. The form of modified regions and their relationship with writing pulse energy and scan speed is examined.

Different methods for stripping cladding light in the high-power fiber laser have been presented. Original fluoroacrylate jacket of fiber selected 50mm-length is continuous removed, then use three different index polymers recoated the selected section to make the uniform light stripping possible. The power-handling capability of the device is tested over 140W cladding light, attenuation of 15dB is achieved and the local temperature does not exceed 70°C.

In this thesis, the currently feedback control algorithms used in the polarization controller, including simulated annealing algorithm and gradient algorithm were analyzed. On this basis, a new method of polarization control feedback algorithm based on fast locating algorithm was proposed to solve the defects of the original algorithm, such as poor convergence and long time consuming search. It can reduce convergence time and improve the response speed of the polarization controllers. This new endless polarization control algorithm using 4-plate polarization controller was proposed and demonstrated. The results showed that the response time of the polarization controller was less than 1ms. The control of polarization was achieved and the output polarization state was stable while the light intensity fluctuated less than 2%, which could run endless reset freely.

A Controllable, high energy, all normal dispersion (ANDi), passively mode-locked Yb-doped fiber laser is demonstrated with a Master Oscillator Power-Amplifier (MOPA) structure. The mode-locking is achieved by nonlinear polarization evolution (NPE). different types of laser pulse are achieved from fundamental mode-locked (FML) single pulse to twin pulse and then to harmonically mode-locked (HML) pulses (the maximum order is 7 times) by adjusting quarter-wave plates (QWPS) and a half-wave plate (HWP) in our system. Using a cascaded long-period fiber grating as the spectral filter, the center wavelength of our laser is fixed at 1034nm.The repetition frequency rate of the FML pulse is 1.53MHz with a pulse width of 817ps. The maximum average energy is 450 mW and the maximum pulse energy of FML single pulse is 294 nJ. Besides, the 517nm green laser output is also achieved by using a LiB₃O⁵ (LBO) crystal as the frequency doubling crystal. The maximum average of the green pulse is 4.71mW.

optical propagation simulation by SG99 code and invert algorithm has been made for two typical laser architecture, namely the National Ignition Facility (model A) and SG-III laser facility (model B) based on measured 400mm aperture Nd:glass slab gain distribution data on ITB system. When the gain nonuniformity is about 5%, 7%, and 9% respectively within 395x395mm² aperture and output beam aperture is 360x360mm², and output energy is about 16kJ/5ns(square) with B-integral limited, 1ω(1053nm) nearfield modulation is about 1.10, 1.15, and 1.30 respectively for model A (11+7 slab configuration), and 1.07, 1.08, and 1.17 respectively for model B (9+9 slab configuration) without spatial gain compensation. With the above three gain nonuniformity and slab configuration unchanged, to achieve flat-in-top output near field, the compensation depth of the input near field is about 1.5:1, 2.0:1, and 6.0:1 respectively for model A, and 1.3:1, 1.4:1, and 3.5:1 respectively for model B. Compared with model A (the beam aperture unchanged in multi-pass amplification), the influence of slab gain nonuniformity on model B (beam aperture changed) is smaller. All the above simulation results deserve further experiment study in the future.

Successful phase-matching methods for Third Harmonics Generation (THG) include phase-matching in birefringent crystal and quasi-phase-matching (QPM) in crystal with periodically poled domains. However, these methods are not feasible in some isotropic materials (e.g. fused silica and photosensitive silicate glass). It was known that volume-grating in isotropic materials can independently generate frequency-converted waves. One of disadvantages of single-layer volumegrating is that the brightness of harmonic emission can not be enhanced by increasing the grating thickness. In this paper, a THG device with stratified sub-gratings was designed to enhance THG in isotropic materials: several sub-gratings were arranged parallel, and the grating-figures misalignment between neighboring sub-gratings was pre-fabricated. In terms of extension of interaction length in THG, our multi-layer sub-grating is formally equivalent to the multi-layer periodically poled crystal (e.g. lithium niobate) in conventional QPM approach. According to the calculation results, the N-layer (N <2) can, in principle, generate TH output intensity of N² times stronger than single-layer volume-grating does, also compared to N times stronger than N-layer without figures-misalignment. The effect of random fabrication error in grating thickness on normalized conversion efficiency was discussed.

A model of 1.2μm Phosphorus doped Raman fiber laser is discussed. It is pumped by a 1.035μm high power Yb-doped dual-cladding fiber laser. The coupled equations for forward and backward stokes waves are set up. An approximate solution for the first –order Stocks laser is obtained by using ‘fsolve’ function in MATLAB which is simply for writing and calculates fast. The relationships between energy conversion efficiency and the length of P-doped fiber, the reflectivity of the output FLM are discussed respectively. And the laser system is optimized.

Coating for double wavelength is one of the important elements in frequency-doubled solid state laser. In this paper, the normal design and whole numerical optimal design were compared. With the same total number of layers, the waviness of coating for double wavelength is more than 0.4139% based on normal design method, while it will be reduced to 0.0109% by whole numerical design, and also the bandwidth can reach 50nm. In experiments, the HfO₂/SiO₂ multilayer films were prepared by IBS. The test results of film designed by the second method show that the transmissivity is above 99% at 532nm, waviness is 0.4%, and the reflectivity is above 99.9% at 1064nm.

In order to investigate the similarity on thermo-mechanical effects by different pulsed beams, this paper conducts a comparison study on the blow-off impulse of aluminum target by pulsed ultraviolet laser and X-ray irradiation. Especially, this paper focuses on the thermo-mechanical effects by pulsed ultraviolet laser and X-ray (blow-off impulse), and build up the scaling relations of impulse coupling with aluminum target by the two pulsed beams within a certain range of energy flux. The study shows that, within the energy flux range of 100~400J/cm², although the mechanisms of blow-off impulse generation of the two pulsed beams are different, the impulse coupling with aluminum target or impulse coupling coefficients of both X-ray and laser have similar scaling relations. Among others, the impulse coupling coefficient of X-ray is larger than that of laser. Based on the comparison of scaling relations, this paper provides the similarity between the two pulsed beams.

Self-organized passive coherent beam combination of multichannel pulsed laser with all-fiber configuration is reported. The phase of multichannel Yb-doped pulsed fiber amplifiers is locked by optical feed-back ring cavity. The traditional disadvantage of energy dissipation to side lode for lower aperture filling is solved via all-fiber laser array with single-aperture configuration. Coherent beam combination of four pulsed fiber amplifiers is experimentally demonstrated. Variable pulsed laser can be obtained by adjusting a AOM,stable combination pulsed fiber laser with excellent temporal and spatial characteristic is achieved. The efficiency of coherent combination is up to 85.0%. This approach presented here provides a feasible technique for power scaling of high-power pulsed fiber laser and maintaining beam quality simultaneously.

Yb-doped fiber lasers (YDFL) have been one of the most widely studied project in last 10 years due to its capability in high power output with excellent beam quality. The optical properties of Yb³⁺ ions in silica glass allow lasing over wide spectral range from 0.98 to 1.2 μm. Up to now, most of the researches focus on YDFL lasing at 1.06-1.12μm, which is most common wavelength band. Actually YFDL operates at other special wavelength bands (i.e., 1.17μm or 1.02μm) are widely required in many application fields. In this paper, we will reports the recent research results of high power YDFL operates at special wavelength. By using Yb³⁺-doped double-clad silicate fiber as the gain medium and commercial pigtailed laser diode as the pump source, we have demonstrated (1) an allfiberizied YDFL operates at 1.12μm, a record output power of 178 W is obtained, the power is further boosted to be 309 W by using one stage of fiber amplifier (2) an all-fiberizied YDFL operates at 1.173 μm, a record output power of 15.7 W is obtained when the pump power is 28 W. (3) an all-fiberizied YDFL operates at 1.018 μm, a record output power of 309 W is obtained when the pump power is 435 W.

In this work an all-fiber linearly-polarized Yb-doped double-clad fiber laser is proposed, in which the resonance cavity is composed of a pair of polarization maintaining fiber Bragg gratings (PM-FBGs). The polarization hole burning is enhanced by the selective polarization feedback by the PM-FBGs. A three-port polarization beam splitter with fiber pigtail was inserted into the laser cavity to select different polarization states. The laser features wavelength of 1069.72 nm and 1069.98 nm, output power of 125 mW, SNR of 45 dB, slope efficiency of 52%, as well as linewidth of 30.7 pm. The polarization characteristics of the laser are studied by measuring the laser power transmitted through a rotating Glan- Thomson polarizer. The degree of polarization of each lasing line is over 12 dB under different pump levels.

A pulse stretcher using chirped fiber Bragg grating is demonstrated. Pulses from a 1053nm mode-locked fiber seed oscillator are multi-stretched by a Linear chirped grating set in a fiber regenerative amplifier structure. We have the pulse stretched from 23.6ps to 378ps after it transmits 3 loops in the stretcher. The major factors which affect the stretched pulse shape are discussed.

Using the flash produced by deflagration of solid pyrotechnics to pump the laser gain medium is a potentially effective way to develop portable high power lasers. The purpose of this work is to examine the effect of some optimization or modifications in terms of compositions and distribution of the pyrotechnic pumping sources on the laser output. The optimization means the transmittance of the output couple. Modifications include: (1) pyrotechnic compositions are improved by adding small amounts of nano Al powders; (2) distribution of pumping light around the laser rod is changed through changing the discrete pyrotechnic tablets into continuous pyrotechnic bars. Results showed that laser output energy reached the maximum of 656 mJ when the transmittance of output mirror raised to10%; after adding nano Al powders into pyrotechnic compositions, laser energy increased by 80% at addition of 2% in the case of discrete distribution, while in the case of continuous distribution, even the mass of pyrotechnics was halved, laser energy still increased to the maximum of 442 mJ with 1% nano Al added. Besides, typical temporal waveform and spot of the laser as well as the light radiation performance of the pyrotechnic tablet are measured to help analyze the laser output performance. It is suggested that the mechanisms of the three modifications we employed are different though they all lead to increase in laser output.

In this paper, we present a compact 803 nm diode side-pumped Nd:YAP laser that can produce 86 W of polarized 1341.4 nm output in continuous-wave mode. The laser characteristics including thermal lens and different cavity types were studied. By comparing the output powers at different resonator lengths and different output couplers, 86 W output power with c-axis polarized laser at 1341.4 nm has been obtained at the maximum pumping power of 840 W. The optical-optical efficiency is 10.2% and the slope efficiency is 16.6%. The beam quality factors of the 1341.4 nm laser are 13.26 and 13.54 in the parallel and perpendicular directions, respectively.

Based upon the scalar wave equation and the equations of hydrodynamics, the simulation model used to calculate the transient thermal blooming of collimated multi-pulse laser by four-dimensional code. Considering the variety of absorption coefficient along with different altitudes, this paper got the new model of repetitively pulsed laser with thermal blooming in tropic by interpolation .On this basis, thermal blooming of different waveforms, such as triangle, gauss, and rectangle were calculated. The paper analyzes the thermal blooming of three waveform laser beams by changing respectively the value of the transmission power. After propagating the same distance in the same condition, the result shows that the peak irradiance of triangular laser distorts least severely; the PIB of gauss laser is the biggest, that is to say, the focusing ability of gauss laser is the best; the center of rectangle laser moves the furthest.

Design of the active region and analysis of temperature sensitivity of high-temperature operating 795-nm special VCSELs for Chip-Scale Atomic Clock (CSAC) are presented. Composition and thickness of the InAlGaAs multiple quantum wells (MQWs) are optimized at room and elevated temperatures. Temperature sensitivity of the threshold current is analyzed by calculating the temperature dependence of cavity-mode gain over a broad temperature range (25°C-150°C). A self-consistent VCSEL model based on quasi 3D finite element analysis is employed to investigate selfheating effects and temperature distribution in the proposed structure. Output power of 2.5mW is expected from 10μm aperture VCSELs at 10mA current at ambient temperature of 358K.