Terahertz emission from indium arsenide excited by femtosecond laser pulses was numerically simulated with the use of
particle method. It is shown that the largest terahertz emission is achieved when 800 nm femtosecond laser pulses are
used for excitation of InAs. We describe terahertz time-domain spectroscopy setup built that uses a relatively simple
terahertz emitter on the basis of indium arsenide plate.
The improved method for calculating the Lyot filter parameters has been developed. The two-plate and three-plate Lyot
filters transmission spectra for the low threshold lasers tuned in the 1100-1300 nm spectral region are computed.
Possible approaches to observe optical bistable behavior of SiO2 opal matrices are discussed. They include mirrorless
schemes exploiting transmission oscillations at the stop-band edge or sharp structure impurity resonances and layouts
with opal inside Fabry-Perot interferometer.
Pump conditions optimization has been performed for one-stage EDFA with three-level forward pumping and quasi-twolevel
backward pumping. The optimization allows to achieve low noise figure, high efficiency of pump power conversion
and sufficiently wide and flat gain spectrum.
Dynamic behavior of the nonlinear Fabry-Perot interferometer with heavily doped n-GaAs internal layer under 20 ns laser pulses excitation has been studied. Optical bistability with less than 10 ns switch-OFF time has been demonstrated.
The lowest pumping threshold of 0,3 W for the LiF:F2- laser has been achieved. The parameters of the Lyot filter used for tuning the LiF:F2- laser have been calculated using the analytical method developed by authors in which the optic path difference in air between incident rays from which the extraordinary and ordinary rays are split off and also the extraordinary ray declining from the incidence plane are taken into consideration.
Design of functional modules of optically reconfigurable routing unit for fiber optical networks is proposed. The peculiarity of these devices consists in realization of optical data transport by means of transverse switching waves in bistable layer. The modules allow to develop gateway units with channel and packet routing of information flows at data rate of ~40 Gb/s and can be scaled up to systems with a higher throughput due to technology of wavelength division multiplexing (WDMDWDM).
The theory of diffraction of planar waves on an extended Fabry-Perot interferometer with transverse sinusoidal and nonsinusoidal modulation of dielectric constant is developed. Calculations of light fields for such systems are realized. Optimal parameters of sinusoidal and nonsinusoidal interferometers-gratings are determined for their usage in devices of amplitude-phase, spatial and spectral modulation of light beams and information signal encoding devices for optical communication channels and networks. A number of devices are proposed where the interferometer-grating can operate as spatial switch due to the intensity redistribution between diffraction orders.
Several types of switches based on optically bistable (OB) thin Fabry-Perot interferometers are reviewed. Applications for time-division multiplexing are proposed and demonstrated experimentally using both separate OB pixels and those coupled by transverse effects in arrays of various types. Compatibility with modern WDM/DWDM fiber optical networks is discussed.
Design of all-optical packet switch with time division multiplexing for channel level of DWDM fiber networks is presented. Main feature of the device is the realization of data buffer on the basis of transverse interconnects within the 2D-array of optically bistable pixels. Functionality of key components of the switch is shown experimentally. Applications of such a device are discussed in the context of data rates and network services.
Information-rate densities in optical communication systems are investigated on the base of the number-state model. Results of numerical simulation show that the considered characteristics increase monotonically with increasing signal power, reducing passband width and environment temperature. For quasi-monochromatic optical communication channels quantum-statistical peculiarities of information carriers can not be taken into account at large enough singal powers when fluctuation noise can be neglected.
Technical parameters and main experimental features of laser complex for investigation of bistable phenomena in GaAs/GaAlAs interferometers and for modeling basic digital devices for optical signal processing (logical elements, switching devices, etc.) are reported.
Algorithms of designing planar shift optical arrays of hexagonal topology on the basis of a 4-pixel switching Y-nodes are considered. Y-node of micrometer size is realized experimentally with the use of optically bistable vacuum deposited ZnS interferometer.
Application of wavelets is investigated with ultimate time-frequency resolution for laser communications. The optimum encoding method for reaching the maximum rate of information transmission is shown to be based on WAVE-wavelets.
All-optical data shift operation in a planar array based on transverse effects in optical bistability in an all-epitaxial GaAs/GaAlAs Fabry-Perot interferometer is reported. Transfer of information bit along a shift register takes about 6 ns.
The theoretical investigations of diffraction of light beams on phase sinusoidal diffraction gratin placed between parallel mirrors of a Fabry-Perot interferometer are carried out. The problem is solved on the basis of Maxwell equations in the approximation of plane waves. The numerical analysis indicates that the power of beam incident on interferometer with a built-in diffraction gratin undergoes strong redistribution between diffraction orders depending on such parameters as angle of incidence, initial detuning for the interference maximum and index of phase modulation. This feature provides the opportunity to use such grating- interferometer as an amplitude-phase modulator and a spatial switch of a new type. If non-linear optical media are used as an intermediate layer and grating is formed by interferencing light beams, then the parameters of such a modulator can be changed and controlled optically.
The maximum achievable characteristics of optical communication systems with different kinds of pulse position modulation have been investigated within the framework of the number-state model. It is shown that the ultimate efficiency in optical systems with ordinary pulse position modulation is determined by the ratio of the number of photons in the signal chip to the number of chips in the signal frame. Maximum achievable efficiencies of all considered methods is compared also. The companions shows that at great values of modulation format the ultimate efficiency of pulse position modulation is higher than that of the multipulse modulation. Overlapping pulse position modulation is shown to be the most favorable one for communication channels. The application of additional encoding to such systems allows to achieve the highest power efficiency of information transmission in optical communication channels.
Dynamics of switching waves in optically bistable all- epitaxial GaAs/GaAlAs Fabry-Perot interferometers is studied experimentally. Realization of planar optical shift register based on propagation of switching waves between neighbor pixels in the plane of bistable layer is proposed.
Principles of formation and controlled propagation of switching autowaves in optically bistable interference structures are considered. On this basis methods and devices are developed for read-in, storing, read-out, switching and transfer of information light signal sin the plane of 2D- arrays of nonlinear optical elements of micron size. A peculiarity of these methods is the possibility of shift data laterally in the array's plane in a direction that is perpendicular to the direction of incident light beams without its interim transformation into electrical signals. This distinctive feature enables developing new architecture concepts of optical information processing systems. Examples of numerical simulations and experimental realizations are presented of optical digital devices with a wide range of functional applications such as Boolean logic elements, shift registers, multiplexers/demultiplexers, basic planar ring processors, etc. The limiting operation parameters of the above devices are discussed.
Both theoretical and experimental analysis is carried out of dynamics describing the information data transfer over the ring by means of switching waves propagating in the plane of bistable layer in direction that is perpendicular to the direction of control and information laser beams. The design and experimental realization is reported of all-optical planar loop circuit demonstrator based on the nonlinear thin-film semiconductor interferometer in the framework of transverse `lock-and-clock' architecture. All-optical and optoelectronic `planar-free space' circuits of such kind can be used for the development and construction of optical systems for digital (and analog) processing, transfer and spatial switching of light information signals.
We investigate some limiting characteristics of two- component optoelectronic system for information transmission on the base of number-state model and Brillouin's negentropy principle. The expression for the upper bound of the capacity of considered communication system is obtained. It is shown, that the capacity of the whole system is substantially limited by the speed characteristics of an optical subsystem. Only in the limited power range of optical signal it is determined by speed of the information transmission in an electronic subsystem. Such a consideration enables us to get deeper insight into the basic principles of information processing in channels with different nature of carriers.
The theory of the diffraction of plane waves on an extended Fabry-Perot interferometer with a phase sinusoidal diffraction grating built-in inside the interferometer is proposed. The theory is constructed on the basis of Maxwell equations in approximation of non-absorptive media. The examples of calculation of distribution of light fields of thin-film interferometers are given in view of all possible orders of a diffraction in a transmission and reflection. It is shown that the properties of investigated systems essentially differ both from properties of interferometers and from properties of the usual holograms without reflecting coatings.
Nonlinear optical absorption in heavily doped n-GaAs and n-InP has been studied experimentally in a nanosecond time scale. Theoretical description of the nonlinear absorption is given that takes into account band-filling, band-gap renormalization and Coulomb screening effects. The results of experimental investigation of self-diffraction effect observed in these semiconductors are presented.
A Nd:YAG Laser IntraCavity SpectroDetector (Nd:YAG LICSD) is described for sensoring small methane (CH4) concentration in the atmosphere. The concentration detectability of the Nd:YAG LICSD of about 0.003 is experimentally demonstrated and of about 1 ppm is discussed.
A new method is presented for shifting optical information signals in the plane of optical bistable array in a direction normal to the direction of incident light beams. All-optical version of shift register and CCD memory device is experimentally demonstrated using semiconductor nonlinear interference filter. The possibility of creating more complicated optically controlled planar circuits and networks is shown.
To our knowledge we report the first fabrication of vacuum deposited thin film interferometers with an intermediate layer doped by quantum-confined semiconductor microcrystallites. These filters demonstrate new spectral and optical properties in addition to those typical for samples deposited by conventional thermal evaporation, and, in particular, high-speed optical switching with picosecond on/off time.
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