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The intracavity second-harmonic generation of laser radiation in an active nonlinear crystal is studied. The spatial distributions of the intensity and power of laser radiation and its second harmonic are calculated by the method of numerical simulations as functions of the parameters of the resonator, active nonlinear crystal, and pump. The analysis is performed for a periodically poled Nd:Mg:LiNbO3 crystal taking diffraction into account.

The results of classical and quantum studies of the laser-radiation self-frequency conversion processes in periodically poled active nonlinear crystals are overviewed. The theoretical and experimental results of studying quasi-phase-matched self-frequency doubling and summation of the laser and pump frequencies in an active nonlinear periodically poled Nd:Mg:LiNbO3 crystal are presented. The possibility of producing frequency-and polarization-entangled states and the sub-Poisson field statistics through a consecutive nonlinear optical frequency conversion in periodically poled nonlinear crystals is considered.

Recent results in the field of three-frequency wave interaction in homogeneous and inhomogeneous (periodically poled) active nonlinear crystals with quadratic nonlinearity are reviewed. The quasiphase-matched processes of self-frequency doubling, self-frequency halving, and frequency mixing of the pump and laser radiations are studied. The consecutive quasi-phase-matched processes of the third-harmonic generation and parametric amplification with low-frequency pumping in periodically poled active nonlinear crystals are also investigated. The analysis is carried out for the case of a periodically poled Nd:Mg:LiNbO3 crystal. Perspectives of using periodically poled active nonlinear crystals in laser devices with self-frequency conversion are discussed.

The theory of intracavity quasi-phase-matched self-frequency conversion in an active nonlinear periodically poled structure is developed. The processes of quasi-phase-matched self-frequency doubling, self-halving and mixing using the pump wave in a periodically poled Nd:Mg:LiNbO{sub 3} crystal are studied. The dependences of the efficiency of nonlinear optical conversion in these processes on the reflection coefficient of the output mirror and on linear losses in the medium are investigated. (nonlinear optical phenomena)

Theoretical and experimental investigations were made of frequency sweeping in a system formed by a highly stable cw master oscillator and a multipass pulsed slab amplifier. It is shown that in a four-pass small-signal amplification system the chirp of the amplified radiation does not exceed 7.7 kHz when the energy of the pump pulses is 36 J and the duration of these pulses is 300 μs.

Quasi-phase-matched second harmonic generation at 542 nm by self-frequency doubling laser radiation at 1084 nm and quasi-phase-matched sum-frequency generation at 464 nm by summing frequencies of laser radiation and of nonabsorbed fraction of diode laser pump radiation at 810 nm are experimentally achieved. These processes are realised in a Q-switched laser based on a periodically poled active nonlinear Nd : Mg : LiNbO3 crystal.

Various grades of steel have been tested for wear under different abrasive conditions. For carbon steels, owing to the increase in hardness and martensite content, wear intensity from Armco Fe to steel U8 decreases by 67%. Maximum wear resistance for dispersion-hardening steels of Cr3Ni3MoV type is achieved when V C = 4 , because of the formation of vanadium carbides. The non-stable austenitic steels with an optimal amount of strain-induced martensite exhibit good wear-resistant properties.

The spatial coherence of the radiation emitted by a single-frequency ring Nd : YAG chip laser with a diode pumping was determined. The maximum value of the degrees coherence was 0.99994±0.00003. The factors limiting the spatial coherence of the radiation of low-power diode-pumped solid-state lasers was discussed.

The intracavity self-frequency conversion of laser radiation in active nonlinear crystal is studied. The spatial distributions of intensities and powers of laser radiation and radiation with conversed frequency are calculated by the method of numerical simulations as functions of parameters of cavity, active nonlinear crystal and pump. The analysis is performed for periodically poled Nd:Mg:LiNbO 3 crystal taking diffraction into account.

We introduce the results of the study of quasi-phase matched processes of self-frequency conversion in periodically poled active nonlinear crystals. The processes of self-frequency doubling and self-frequency summing have been experimentally realized and studied in periodically poled Nd:Mg:LiNbO 3 crystals in CW and Q-switched regimes. The theory of self-frequency conversion has developed. The results of theory are in good agreement with experiments.

We introduce the results of the study of intracavity quasi-phase-matched three-frequency wave interactions in active nonlinear periodically poled crystals. The process of self-frequency summing in periodically poled Nd:Mg:LiNbO 3 has been studied. Quasi-phase-matched sum-frequency generation at 0.464 μm by self-frequency summing of fundamental radiation at 1.084 μm and unabsorbed part of pump radiation of diode laser at 0.810 μm in periodically poled Nd:Mg:LiNbO 3 crystal has been realized experimentally.

We introduce the theory of intracavity quasi-phase-matched three-frequency wave interactions in active-nonlinear periodically poled medium, and in particular, self-frequency doubling and halving. The combination of laser oscillation of active ions with nonlinear optical properties of the host material provides an opportunity for creation laser with self- frequency conversion. Quasi-phase-matched second harmonic generation at 0.542 micrometer by self-frequency doubling of fundamental radiation laser radiation at 1.084 micrometer in periodically poled Nd:Mg:LiNbO3 crystal pumping by diode laser at 0.810 micrometer has been observed experimentally.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present results of theoretical and experimental investigations of frequency sweeping mechanisms of the narrowline diode-pumped monolithic ring Nd:YAG laser radiation in multipass pulsed slab amplifier. The obtained value of the maximal chirp in the four-pass slab amplifier does not exceed 7.7 kHz when energy of the pump pulses is 36 J and the duration of these pulses is 0.3 ms.

We present results of precise measurement of spatial coherence degree and depolarization degree of the single frequency diode-pumped monolithic ring Nd:YAG laser radiation. An analysis is made of the factors influencing the spatial coherence and depolarization of miniature lasers with longitudinal diode pumping.

For the first time depolarization degree of the diode-pumped monolithic ring Nd3+:YAG laser has been measured. The obtained value of depolarization degree equals 3 (DOT) 10-3. It has been shown that the dominant mechanism of the intracavity losses and the output light depolarization is diffraction on random inhomogeneities of birefringence in the laser media.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The intracavity summing of the frequencies of lasing (λ = 1.084 μm) and pump radiation from a 0.81-μm diode laser is performed in a periodically poled active nonlinear Nd:Mg:LiNbO3 crystal.

The possibility of the quasi-phase-matched generation of the second harmonic (λ = 0.542 μm) by self-doubling of the fundamental radiation frequency in an Nd:Mg:LiNbO3 crystal laser having a regular domain structure and pumped by a diode laser (λpump = 0.81 μm) was demonstrated.

Consecutive generation of the third harmonic (i.e. generation of radiation with the doubled frequency followed by frequency summation) radiation from a Q-switched Nd:YAG laser (λ = 1.064 μm) was observed in a Y:LiNbO3 crystal polarised periodically along the z axis. The modulation period of the nonlinear susceptibility was ~ 60 μm. The second and third harmonics of the radiation were generated respectively in the ninth and thirty-third quasi-phase-matching orders.

The degree of depolarisation of radiation from a single-frequency ring monolithic diode-pumped(chip) Nd3+:YAG laser was measured for the first time: its value was 3×10-3. The dominant mechanism of intracavity losses and of depolarisation of the output radiation was diffraction by random inhomogeneities of the birefringence of the active element.

We have investigated linear diode-pumped YAG lasers with matching optics provided by specially shaped gradient lenses for various choices of active-element length and output-mirror transmission coefficient. For these lasers we obtained single-frequency lasing on the lowest transverse mode at a power of 40 μW. The laser linewidth, which was measured by a heterodyne method was 10 kHz.

It is shown that materials with different physical properties are characterized by different widths of the linear part of the dependence of the charge reaching the slit of a mass-spectrograph monitor on the number of laser pulses. This difference and the change in the ratio of singly and doubly charged ions in the analytic part of a mass spectrograph are determined by the shape of the craters formed as a result of the interaction of laser radiation with the investigated material.

A solid-state laser was developed on the basis of a highly stable cw narrow-band monolithic YAG laser pumped by semi-conductor diode lasers, a system for shaping a pulse of given duration, and a multipass slab amplifier. The spectral and power characteristics of the YAG laser acting as a master oscillator were investigated. An interferometric study was made of the thermal distortions of the laser beam in the slab amplifier where the ray paths were zigzag-shaped. The signal from the master oscillator was amplified by a factor of 7×104 in the four-pass slab amplifier without distortion of the spatial characteristics of the laser beam.