The efficiency of excitation of surface plasmons upon noncollinear light scattering from a metal diffraction grating is studied. It is shown that this efficiency strongly depends on the grating profile and the azimuthal angle of rotation. The relation between the spatial configuration of the electromagnetic field near the grating-vacuum interface and the possibility of excitation of plasmons is found. Taking into account different conditions for plasmon excitation, the peculiarities of experimental angular dependences of specular reflection are explained.
An analysis is made of the effects of reflection and absorption of radiation in an optical parametric converter used to measure the absolute spectral density of the energy brightness with a quantum photometer. A universal method is proposed for calculating a correction factor which eliminates systematic errors that can appear when the brightness is measured by parametric conversion in a crystal where the signal, measured, or pump waves experience absorption and reflection. Expressions for the correction factor are obtained for converters of different geometry. These expressions give the factor in terms of the absorption and reflection coefficients of the faces of a crystal for all the waves participating in the parametric interaction process.
Large crystals of silver selenogallate were grown. Generation of the second harmonic of CO2 laser radiation in these crystals was studied. An energy conversion efficiency of 19.8% was achieved. Calculations were made of the angular tuning characteristics of optical parametric oscillators using type I and II processes at various pump wavelengths.
An experimental investigation was made of the mutual influence of an optical breakdown and stimulated Raman backscattering. A study was made of the various regimes of mutual discrimination of these processes, ranging from complete suppression of the scattering by an optical breakdown to suppression of the breakdown by depletion of the pump radiation due to the scattering. A study was made of the characteristics of stimulated Raman scattering in the presence of an optical breakdown.
An MF-14 photodiode array was used to determine the radiation field of pulsed ultraviolet lasers. The responsivity of this array at the wavelength of 0.337 μm was S = 4 × 108 V/J. The distributions of the radiation from an N2 laser were determined in the near-field zone. The distributions were also obtained for XeF, XeCl, and KrF excimer lasers in the far-field zone. The angular dimensions of the distributions were determined.
Experimental and numerical investigations were made of the stimulated emission regimes of two coupled CO2 lasers with different resonators. A difference between the resonator lengths amounting to λ /2 could give rise to two locking regions when a cophasal mode was emitted in one region and an antiphasal mode in another. A selective iteration method was used to find a range of parameters ensuring single-mode emission from the coupled lasers. The results of the calculations were in good agreement with the experiments.
A theoretical analysis of the operation of lasers utilizing vibrational-rotational transitions in diatomic anharmonic molecules was made taking into account the finite nature of the rotational relaxation rate. The conditions of validity of the equivalent two-level model describing these lasers were identified. Expressions for the populations of the upper and lower states participating in the lasing transition were derived using this model. Numerical calculations were made of the characteristics of an H2–F2 chemical laser using multilevel and two-level models and the results of the calculations were compared.
High density compression of main fuel and stable formation of hot spark at the center of imploded core have been investigated to obtain the scaling and the requirements for fusion ignition and high gain. For this purpose, the experimental data of the high density compression up to 600 times solid density with hollow shell pellet have been analyzed and compared with simulations.
A numerical analysis is made of the dynamics of self-initiation of ultrashort pulse generation in cw solid-state lasers with mode locking in an additional resonator cavity. Phase self-modulation in the main or additional resonators is postulated. It is shown that generation of stable ultrashort pulse trains from the spontaneous noise is possible in limited ranges of the laser parameters. It is shown that how these ranges transform in the pump intensity - coupling parameter plane, depending on the phase self-modulation parameter, on the width of the pass band of a spectral filter, and on the cross section of the lasing transition in the active medium.
A quantitative physical model of metal cutting by cw laser radiation in the absence of chemical reactions was developed. An experimental study was made of the flow of the processing gas using a geometrically similar model. The distributions of the pressure and velocity of the gas were determined at the cutting front. Simplified mathematical algorithms for the thermal problem were constructed and calculations were made of the maximum depth of the cut (kerf) and cutting speed as functions of the laser beam parameters. Possible nonsteady-state characteristics of the motion of the melt and of the cutting front were considered. A thermal mechanism was proposed for the formation of the regular rippling of the kerf, based on a balance between capillary forces and forces exerted on the melt by the gas stream in the vicinity of the upper edge of the cutting front. Simple formulas were obtained for calculating the depth and period of the ripples.
The problem of controlling the transmission of optical radiation through a randomly inhomogeneous medium is investigated for the case in which complete a priori information on the statistical properties of the propagation channel is available. An optimal control algorithm is found for adaptive-optics systems for an arbitrary ratio of the observation time interval to the coherence time of the propagation channel. Both cw and pulsed probe regimes are discussed. An estimate is obtained for the efficiency of this optimal algorithm for the steady adaptation state.
A concept of similarity of processes in systems of coupled nonlinear waveguides and coupled nonlinear resonators is employed to consider the behavior of waveguide systems under various excitation conditions. The results obtained are used for development of a new optical gate which corresponds to the nonlinear Fabry-Perot resonator.
Some important problems concerning the profiling of the potential energy in quantum-well lasers are discussed. The goals being sought are to introduce a relative shift of the levels of localized states, to introduce an energy gap, and to reduce the transmission of barriers without increasing their height.
An analysis of an equivalent system of a resonator consisting of many tilted reflecting planes is used to calculate the distribution of the energy in the output beam. The results show that the divergence can be reduced by ensuring that the tilts of the exit and totally reflecting mirrors are small. A new type of a resonant reflector is described.
It is predicted theoretically that the efficiency of self-mode locking can be raised by means of a bleachable shutter in the main cavity or an auxiliary cavity. The laser emits a stable train of ultrashort pulses under these conditions. The theory is based on a fluctuation model of the operation of a cw solid-state laser with a linear auxiliary cavity. The increase in efficiency involves a broadening of the region of parameter values of the system in which self-mode locking occurs, a significant decrease in the threshold pump intensity, and a reduced sensitivity of the operation to the phase mismatch of the lengths of the cavities. It is shown, for the first time, that a stable train of double ultrashort pulses can be generated by a system with a shutter in the auxiliary cavity. It is also shown that a self-mode locking is possible in the case in which there is a phase mismatch of the cavity lengths and there is no phase self-modulation in the main cavity.
The transfer of energy from Tm3+ to Ho3+ ions and also the interaction between excited Tm3+ ions and excited Tm3+ and Ho3+ ions in YSGG:Cr3+:Tm3+:Ho3+ and YSGG:Cr3+:Tm3+ crystals were studied quantitatively. The influence of these processes on the operation of two-micron lasers was analyzed.
A new approach is developed for the description of self-modulated operation of solid-state ring lasers. This type of operation is considered as a superposition of two normal modes of a ring resonator with retroreflectors. The normal modes of ring resonators with retroreflectors are found using the 4 × 4 matrix formalism. The frequency characteristics of rotating nonplanar ring lasers, including monolithic chip lasers, are calculated.
