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The phenomena of optical bistability, hysteresis and memory under the interaction of oppositely directed (OD) light waves in a CW YAG:Nd3+ solid state ring laser (SRL) have been experimentally discovered. The possibilities of spontaneous or forced (with modulated SRL parameters) commutation of the radiation direction without transients at the relaxation frequency (typical for solid state lasers) have been established both in the single-mode and in the mode-locking regimes with various feedback circuits. The mode-locking band was found to be substantially broadened by more than an order of magnitude when OD light waves primarily diffracted on a standing ultrasonic wave were returned into the acousto-optical modulator. With such acousto-optical feedback the mode-locking regime has been obtained using a modulator on a running ultrasonic wave.

The EPR spectra of PO 4 2− and PO 3 2− and atomic hydrogen were observed in γ-irradiated (Li-TRx-La1−x) — phosphate glasses, where TR = Nd, Sm, Er. Using the obtained data on the atomic hydrogen EPR spectrum the estimation of the OH− group concentration was made for these glasses.

It is found experimentally that the competitive interaction of the oppositely directed (OD) light waves in YAG:Nd3+ and ruby solid-state ring lasers OIRL) can be significantly reduced due to nonlinear optical effects (second harmonic generation, stimulated Raman scattering, resonant absorption) since the nonlinear losses for the wave of lower intensity are lower. It was established that in the SRL with a resonantly absorbing medium the spatially inhomogeneous burning-out and the slowness of the relaxation of the inverted population in the solid-state active medium may result in strong phase nonreciprocity due to the frequency shift of the OD waves after their reflection from the moving lattice of the inverted population. The beat frequency strongly depends on detuning between the gain and absorption lines and may be more than two orders of magnitude less in comparison with the resonator frequency difference in the rotating SRL. The possibility has been shown of active stabilization of the bidirectional generation in the beat regime using the nonreciprocal amplitude Faraday element controlled by the external feedback circuit via the difference of the OD waves intensities.

Reversible optical bleaching of the induced absorption was observed and investigated in the range 0.5–1.3 μ for γ-irradiated glass fiber waveguides. The bleaching was produced by He-Ne laser radiation (γ = 0.63 μ). The effect was associated with an induced absorption band characterized by-a maximum in the range ~0.9 μ.

An investigation was made of the profile of the hyperfine component of the cesium line observed using a cw semiconductor laser. It was found that the profiles of the absorption and luminescence signals, their widths, amplitudes, and the positions of the maximum depend strongly on the relaxation time of the active medium, laser radiation intensity, and rate and direction of passage of the frequency through resonance.

Passive mode locking was achieved for the first time in a cw solid-state YAG:Nd3+ laser using a filter based on the use of an LiF crystal with color centers as the saturable absorber. A study was made of the effect of the filter density on the lasing dynamics.

An investigation was made of the radiation-optical stability of SiO2:GeO2–SiO2 and SiO2–SiO2:B2O3 glassfiber waveguides. The induced absorption spectra in the 0.45–1.75 μ wavelength range were obtained by altering the gamma-radiation dose between 103 and 108 rad. An investigation was made of the growth kinetics of the induced absorption of the waveguides during gamma irradiation and of the induced absorption decay kinetics after irradiation.

Theoretical and experimental investigations were made of the properties of a solid-state ring laser in the case of kinematic modulation of the resonator length. It is shown that the observed characteristics can be explained only if we allow for the combined influence of the variable-sign frequency offset and modulation of the coupling between the opposite waves.

It was found experimentally that a laser with a resonator containing a section of a multimode fiber waveguide exhibited a characteristic frequency selection, which made it possible to control the emission spectrum. The effects observed were explained qualitatively.

A theoretical analysis is made of forced mode locking in a cw solid-state laser having a homogeneously broadened luminescence line allowing for nonlinearity of the active-medium gain. An algebraic system of equations whose solutions define the steady-state parameters of the output radiation was derived assuming that a weakly asymmetric quasi-Gaussian pulse propagates in the resonator.

A new method for determining the optical nonreciprocity is suggested and analyzed. The method is based on the use of a ring laser operating in the self-modulation regime with a variable-sign frequency ''pedestal.'' The example of a ring YAG laser is used to show that this method should make it possible to reduce greatly the experimental error.

Locking of longitudinal modes in a cw solid-state laser by the use of a saturable absorber was demonstrated experimentally for the first time. A study was made of the dependence of the nature of lasing on the density of the absorber.

A determination was made of the relationship between the luminescence energies of the transitions from the $sup 4$F$sub 3$/$sub 2$ metastable state to the $sup 4$I$sub 9$/$sub 2$, $sup 4$I$sub 11$/$sub 2$, and $sup 4$I$sub 13$/$sub 2$ levels of Nd$sup 3+$ in silicate and phosphate glasses, characterized by a high directionality of laser radiation. The results of these measurements were compared with the data obtained for some mass-produced glasses. It was found that the variation of the composition within one base could alter the ratio of the luminescence energies of the two main bands (corresponding to the transitions from $sup 4$F$sub 3$/$sub 2$ to $sup 4$I$sub 9$/$sub 2$ and $sup 4$I$sub 11$/$sub 2$) by 10--15% and when the base of the glass was altered, this ratio could change by 30--35%.

It was found experimentally that combination of passive and kinematic mode locking in a cw YAG:Nd laser made it possible to extend the separate capabilities of each of these methods, and to generate ultrashort pulses with stable amplitudes and durations.

Yttrium aluminum garnet laser with a waveguide in its resonator was constructed. The time characteristics of the output of this laser were investigated under free-oscillation conditions using resonators of different effective lengths. Locking of axial modes was observed when the waveguide was sufficiently long. The nature of the distribution of the output radiation in a plane perpendicular to the resonator axis was investigated.

Locking of cascade components of stimulated Brillouin scattering, excited in a multimode fiber waveguide, was achieved for the first time. It is postulated that a new type of intermode wave phase matching is responsible for such locking.

Computer calculations are used to investigate the properties of multilayer dielectric mirrors over a wide spectral range greater than the width of the region of high reflection. Distributions of the electric field and radiation energy over the coating thickness are obtained. These determine the spectral dependences of the optical strength and loss factor of the mirror. Recommendations are given on the optimum use of dielectric mirrors. A method is proposed to determine small loss factors of high-reflection dielectric mirrors. This involves measuring, with normal photometric accuracy, the reflection and transmission coefficients at two resonance points close to the high-reflection plateau, where the mirror loss factor is more than an order of magnitude higher than its value in the region of maximum reflection.

The first cw YAG:Nd3+ laser with a ring resonator, formed by a fiber waveguide up to 20 m long, was constructed. A study was made of the principal characteristics of this laser. The interaction between the opposite waves and the lasing regimes and characteristics can be controlled by deformation of the fiber.