High power GaN-based laser diodes (LDs) are very desirable for various applications such as optical storage systems. We have obtained GaN films of low dislocation density using epitaxial lateral overgrowth technique and the raised- pressure metalorganic chemical vapor deposition technique. Dislocation density of the improved GaN is about 10⁷ cm^-2. Optimized GaN-based LDs fabricated on the improved GaN films have operated up to 35 mW without any kink. The lifetime is more than 500 hours with a constant power of 20 mW at 25 degree(s)C under continuous wave conditions. Furthermore, we have introduced buried-ridge laser diode structure in order to control the optical transverse mode. The features of the far field patterns of LDs with AlGaN burying layers indicate their controllability.

The optical confinement and related issues are considered of novel semiconductor laser structures based on III-group nitrides. The approach of normal modes is used in an analysis of the InGaN-based laser diode that is actually a set of coupled waveguides. Laser emission mode is found to be subjected to internal mode coupling. When phase velocities are close in coupled modes, the interaction is resonantly strong, and produces a significant modification of both the spatial mode configuration and laser threshold. Particularly, the modal gain can be quenched totally keeping the material gain at high level. Therefore such resonance is an important issue in the nitride-based laser designing. Also, the modeling of nitride-based VCSEL is performed using an effective frequency method and laser operation is simulated numerically. The thermal lens effect is shown to be important in the mode formation.

A simple way to generate wavelength tunable ((Delta) (lambda) > 50 nm) semiconductor laser pulses with a width of a few hundred femtoseconds and a timing jitter well below 1 ps is self-seeding of a gain-switched Fabry-Perot laser diode with subsequent chirp compensation and soliton compression. The low timing jitter of the single mode laser pulses allows self-seeding to be used e.g. in high temporal resolution electro-optic sampling systems. Additionally, by controlling the electrical phase delay between two self seeded laser diodes femtosecond pulses with electrically adjustable time delay can be generated.

We propose a relatively simple dynamic laser model based upon continuity equations for electron and hole concentrations, energy balance equation and a set of rate equations describing spectrally dependent photon density. These equations are solved in a self-consistent way together with Poisson equation. The model assumes that characteristic times of establishing the carrier temperature are shorter than those of carrier-to-phonon interaction. Using this model, the dynamic response of AlGaAs/GaAs double heterostructure laser is analyzed at current densities up to approximately 6 X 10⁴ A/cm². It is shown that the reaction of carrier temperature to the appearance of optical pulse is spatially nonuniform and is determined by the balance of the heating induced by the stimulated emission and the cooling associated with carrier and heat transfer across the active layer.

Great differences were found between the spectral and power responses for two modes of a single-heterostructure laser operation, with the dynamic behavior of each mode fitted to the traditional definition of the internal Q-switching phenomenon. The first mode is interpreted in terms of the most popular diffraction losses theory, while the other one is related to the practically important method of high-power picosecond optical pulse generation and interpreted in terms of a recent carrier heating and cooling model. This finding could obviate confusion in the interpretation of mechanisms of high-power picosecond pulse generation in the Q-switching mode.

A compact laser diode based transmitter was designed and tested for laser radar and various laboratory applications. Single optical pulses with a peak power of up to 200 W, 23 - 65 ps pulse duration and a repetition rate of up to 50 kHz were measured. Transient mode spectral filtering suppressed afterpulsing modes by a factor of 10⁴ - 10⁵ with respect to the peak power. A control module was developed which provided a jitter value between electrical triggering and the optical pulses as low as 14 ps. Averaging of 10³ events allows 1.5 ps stability between the triggering and the optical pulses to be achieved within a delay range from 5 to 250 ns.

We show that in addition to the dispersion mechanism of selection of tilted waves in a cavity of a broad-area VCSEL the dependence of the reflection from distributed Bragg reflectors on an incidence angle of the tilted waves leads to the mode selection and spatial periodic pattern formation. The mode competition may acquire even more diversity if the polarization of the laser field comes into play.

We find three types of complex polarization dynamics arising in VCSELs with polarized optical feedback when axes of the intrinsic and external anisotropies are aligned. Their appearance depends on the interplay between these anisotropies which determines the stability of modes polarized along the polarizer axis with respect to perturbations with the same and orthogonal polarization. The influence on the laser behavior of a rotation of the external polarizer is considered.

Cavity solitons appear as stationary, isolated peaks of light superimposed onto a homogeneous background field in the transverse profile of the coherent field transmitted or reflected by a non-linear resonator. These self-organized structures are theoretically predicted and simulated in a broad area multi-quantum-well vertical microresonator. We develop models suited to describe the macroscopic properties of the medium and the nonlinear interaction with the coherent field. Parametric domains and operational regimes for stable solitons are investigated along with some quantitative appreciation of their characteristics. Intrinsic stability properties of solitons are investigated by means of semi-analytical techniques and this allows to describe the destabilizing mechanisms for solitons, mutual interaction properties, their response to perturbations and some of their dynamical features.

The theoretical and numerical modeling of the light beams transverse structure formation upon coherent interaction in the interferometers with resonant nonlinearity has been proposed. The analysis has been performed on the base of the model theory for the scheme of counterpropagating beams in the ring cavity and for the scheme of oblique symmetrical incidence of two beams on the Fabry-Perot interferometer. Complex spatial-temporal evolution of the light beams structure, such as formation of bound states, symmetry breaking instability, asymmetrical self-oscillations has been demonstrated.

Multiple pulse operation of passive mode-locked lasers with nonlinear refractive index of intracavity elements has been investigated. The hysteresis dependence of number of pulses in established regime on the pump power has been found. It is shown that this number depends also on initial condition of generation. The application of discovered multistability and hysteresis to optical communications and information processing is discussed.

Paper presents the results of theoretical study and numerical simulations of the laser bullets--3D dissipative optical solitons in continuous media with saturable resonance amplification and absorption, constant (non- resonant) absorption, and quadratic frequency dispersion. We have performed bifurcation analysis of stationary symmetric bullets, have determined conditions of their existence in dependence of frequency detunings, investigated possibility of existence of topological 3D dissipative solitons, and studied different regimes of interaction of two laser bullets.

The features of spatial and temporal evolution of two short laser pulses propagating in three-level medium under conditions of coherent population trapping and adiabatic population transfer is investigated in adiabatic approximation. It is shown that in both cases pulses can penetrate into a medium at a distance considerably exceeding the length of linear absorption of a single weak probe pulse in absence of a coupling pulse at adjacent transition. The difference of spatial and temporal evolution of level populations in processes of coherent population trapping and adiabatic population transfer is demonstrated. Also we show that the concept of dressed-field pulses is consequence of Manley-Raw relation.

System of evolution equations describing ultra-short optical pulse propagation in quadratic non-linear medium is derived with taking into account the dispersion of the non-linear susceptibility and second-order group-velocity dispersion. Both type I and type II of phase matching were considered. The case of a finite phase mismatch was analyzed by an analytical method. The steady state pulses of the fundamental and second harmonic waves were found. There are new kinds of ultra-short pulses propagating in quadratic medium in the anomalous and normal dispersion regime.

We observed and investigated self-starting quasi-periodic pulsation in Er-doped fiber laser at 30 - 100 mW pump power. Pulse with duration of 10 - 50 ns and peak power of 50 - 200 W are generated at a quite stable repetition rate in the range of 300 - 500 microsecond(s) . In contrast with previous experiments the pump level in our experiment is significantly lower. At this low pump power we found no nonlinear effect except SBS influencing on the laser dynamics. The experimental results were explained by a theoretical model based on cooperative dynamics of Rayleigh backscattering and Stimulated Brillouin Scattering (SBS). Using digital oscilloscope, we traced in details different stages of Q-switching pulse formation process: growth of the spontaneous radiation, lasing due to Rayleigh backscattering, appearance and growth of the first order SBS Stokes radiation and the second order Stokes radiation, lasing suppression due to saturation of the population inversion in Er-doped fiber by the SBS Stokes radiation. Good agreement between theory and experiment have been demonstrated.

We report the evidence a novel phenomenon which is observed in VCSELs working in a bistable region, that we have called Noise Assisted Binary Information Transmission: the addition of noise to the pump current up to an optimal value leads to a strong improvement of the transmission quality, measured by the Bit Error Rate. We analyze different indicators to define the output string and the comparison of the input with the output signal is eventually reduced to a comparison of binary strings and can treated by means of standard methods of information theory. These results represent the first experimental evidence of Aperiodic Stochastic Resonance. We analyze the possible application to optical communications and compare it to a standard amplitude modulation scheme.

Cancellation of excess noise of quantum optical solitons is based on successive passage of a soliton through an optical fiber with positive nonlinearity and negative dispersion and then through a near-resonant two-level systems with negative nonlinearity and positive dispersion. An evolution of a quantum fluctuation in one medium will be reversed in the other. In such a way, the unwanted excess noise due to self- phase modulation in optical fibers can be fully suppressed leading to a radical improvement of accuracy of quantum nondemolition measurements of optical solitons. A detailed discussion of the compensation method with thorough numerical estimations for existing resonant media is provided.

Numerical solutions are obtained of the full self-consistent system of equations for the counter rotating polarization components of the field of short optical pulse propagating in birefringent non-linear fiber and the ensemble of the energy level degenerated dopant resonance atoms implanted in fiber material. In every cross-section of fiber the ellipticity of the polarized wave experiences a complex evolution in time accompanied by rapid changes of the azimuth angle due to interplay of dispersion and Kerr non- linear self- and cross-modulation. The reciprocal effect of the impurities on the traveling pulse causes the oscillations of the pulse envelope able to distort completely the shape of the input signal, while the resonance absorption can drive the birefringence from the non-linear back to linear regime.

We model upconversion and migration in an ensemble of inhomogeneously distributed erbium ions. Treating Er- clusters as fractal objects we find the dependence of the upconversion rate on the population inversion for different fractal dimensions.

Bragg gratings were written in H₂-loaded polarization- maintaining fiber (PM-FBGs) and inserted in an actively mode-locked Er-doped fiber laser. The use of PM-FBG in sigma laser cavity allows to effectively build all polarization- maintaining fiber laser. Long term stabilization of the laser was ensured by a feedback loop that controlled the cavity length. Peak wavelengths, reflection bandwidths and reflectivity values of the grating were equal to 1545.5 nm and 1540.5 nm, 1.6-nm and 0.8-nm, of 99% and 90%, respectively. At a 3-GHz repetition rate, pulses of 9.4-ps and 27.9-ps duration were generated with first and second gratings, respectively. By inserting additional long piece of dispersion-shifted fiber in the cavity, nonlinear pulse shortening was observed due to formation of average soliton inside the cavity. In this case, pulses of 7.8-ps and 22.7- ps duration were generated with first and second gratings, respectively. With the first grating, generated pulses were close to transform limit for hyperbolic secant pulse shape. Longer pulse duration obtained with second grating is attributed to narrower bandwidth and residual chirp of the grating.

We demonstrate for the first time that pulse-to-pulse amplitude fluctuations occurring in the rational-harmonic repetition-rate-doubling regime of actively mode-locked fiber laser are eliminated when modulation frequency is properly tuned. Irregularity of the pulse position in the train is found to be the only drawback of this technique. The irregularity can be reduced to value acceptable for applications by a proper laser design.

The initial field amplitude (alpha) ₀, normalized to the amplitude of a fundamental soliton, and the ratio (Gamma) of the dispersion distance to the loss distance are successfully used to classify the areas of originating the `light' solitary waves of the first order in optical systems belonging to Landau-Ginzburg type. We analyze the model, described by the complex cubic Landau-Ginzburg equation in a reduced form, and demonstrate for the first time that the guiding-center solitons, associated usually with the interval of (alpha) ₀ (epsilon) [1.0;1.5], (Gamma) >= 1, can exist even if (Gamma) <EQ 1. The application of peculiarities inherent in picosecond optical guiding- center solitons of the first order to the problem of creating a fiber network for a precise synchronization is proposed and discussed.

This paper presents a brief review of developments in modern wireless communication technology--free-space laser communication--both for intersatellite and terrestrial applications, including some Russian designs. The character of the Russian intersatellite terminal is its modular design and excluding of almost all opto-electronic instruments out of optical module, with duplex transfer of optical signals between components through fiber-optic cables. Such a design reduces the weight of stirring parts significantly and facilitates alignment. As for terrestrial lasercom, several commercial systems are listed, and results of link availability calculations (for Moscow region weather conditions) are presented.