For the first time to our knowledge, a single-phase solid solution Sr(MoO_4) 0.8 (WO_4) 0.2 was used as an active medium of a Raman laser. Using the high-intensity synchronous picosecond pumping satisfying the condition of phase capture of the parametric Raman interaction on the second vibrational mode made it possible to oscillate six components of Raman radiation with a combined frequency shift on the first (888 cm -1 ) and second (327 cm -1 ) vibrational modes in the wavelength range of 1194-1396 nm. Oscillation efficiency of the multiwavelength Raman laser radiation was as high as 10%. By detuning the Raman laser cavity length, the pulse shortening down to 6 ps for the Raman laser radiation components with the combined frequency shift was obtained, which is an order of magnitude shorter than the pumping pulse duration (64 ps). Keywords: stimulated Raman scattering, single-phase solid solution, vibrational mode, synchronous pumping.

Graphene-mode-locked solid-state lasers usually have a low optical efficiency (<10%) or a low output average power (<1W) due to losses in the graphene saturable absorber and the thermal load of the laser crystal. We demonstrate what we believe to our knowledge is an improved design for a highly efficient, powerful, diode-end-pumped Nd:YAG laser mode-locked with graphene. Internal losses of the laser cavity were minimized by using a high-quality monolayer graphene saturable absorber applied directly on the cavity end mirror. In comparison to other graphene-mode-locked solid-state lasers, the record high optical-to-optical and slope efficiencies of 19.1 and 24.5%, respectively, in a continuous wave mode-locking regime were achieved. The highest output average power was as high as 1.7 W for the ultrashort pulse repetition rate of 82 MHz at the beam quality of M 2 =1.3×1.4.

В настоящей работе представлены результаты исследований генерации лазера на композитном элементе из Nd3+:YAG/Cr4+:YAG керамики отечественного производства. Композитный элемент, полученный методом реактивного спекания смеси порошков оксидов, состоит из двух частей – активной среды Nd3+:YAG и пассивного лазерного затвора Cr4+:YAG. В режиме пассивной модуляции добротности реализована генерация излучения со средней мощностью 4,2 Вт. При этом длительность и частота следования импульсов составили 4,6 нс и 68,5 кГц соответственно. С использованием исследуемого лазера в работе реализован процесс взаимодействия лазерного излучения с материалом из нержавеющей стали марки AISI 304 в воздушной и в жидкостной средах. В результате лазерного воздействия на поверхности материала образуются кратеры, а жидкость содержит синтезируемые микро- наночастцы. Таким образом, в работе впервые экспериментально продемонстрирована возможность использования лазера на Nd3+:YAG/Cr4+:YAG керамике для обработки поверхности материала и получения наноразмерных частиц на примере абляции нержавеющей стали AISI 304 в жидкости. Полученные в работе результаты могут быть интересны для решения задач технологической микрообработки материалов и получения частиц различной дисперстности. This paper presents the results of studying laser generation on a domestically produced composite element made of Nd3+:YAG/Cr4+:YAG ceramics. The composite element obtained by reactive sintering of a mixture of oxide powders consists of two parts – an Nd3+:YAG active medium and a Cr4+:YAG passive laser shutter. In the passive Q-switching mode, generation of radiation with an average power of 4.2 W was realized. The pulse duration and repetition rate were 4.6 ns and 68.5 kHz, respectively. Using the laser under study, the process of interaction of laser radiation with AISI 304 stainless steel in air and liquid environments was realized in the work. As a result of laser action, craters are formed on the surface of the material, and the liquid contains synthesized micro- and nanoparticles. Thus, the work has experimentally demonstrated for the first time the possibility of using a laser on Nd3+:YAG/Cr4+:YAG ceramics for processing the surface of a material and obtaining nanosized particles using the example of ablation of AISI 304 stainless steel in liquid. The results obtained in the work may be of interest for solving problems of technological microprocessing of materials and obtaining particles of various dispersions.

For the first time to our knowledge, a single-phase solid solution Sr(MoO4)0.8(WO4)0.2 was used as an active medium of a Raman laser. Using the high-intensity synchronous picosecond pumping satisfying the condition of phase capture of the parametric Raman interaction on the second vibrational mode made it possible to oscillate six components of Raman radiation with a combined frequency shift on the first (888 cm–1) and second (327 cm–1) vibrational modes in the wavelength range of 1194-1396 nm. Oscillation efficiency of the multiwavelength Raman laser radiation was as high as 10%. By detuning the Raman laser cavity length, the pulse shortening down to 6 ps for the Raman laser radiation components with the combined frequency shift was obtained, which is an order of magnitude shorter than the pumping pulse duration (64 ps).

Theoretical and experimental studies were conducted on providing conditions for the generation of multiple radiation components with a small wavelength spacing in a crystalline synchronously pumped SRS laser with combined frequency shift on high-frequency and low-frequency vibrational modes of an SRS-active crystal. A theoretical analysis has shown an important role of four-wave parametric Raman interactions on the low-frequency vibrational mode of the crystal provided the conditions of coherence and of nonlinear phase capture of such interactions are satisfied. For the first time, SRS generation was carried out at five closely spaced wavelengths of 1194, 1242, 1294, 1336, and 1396 nm in a SrMoO 4 crystal under synchronous pumping by a high intensity picosecond YAlO 3 :Nd 3+ laser at a wavelength of 1079 nm satisfying the condition of nonlinear phase capture.

We propose and study the conditions of zero-dispersion phase matching for parametric Raman interactions in birefringent crystals differing by anisotropy of zero-dispersion wavelength and allowing for the spectral tuning of the zero-dispersion phase-matching condition. We choose a highly birefringent crystal of calcite having a wide zero-dispersion anisotropy range for the demonstration of new effects of laser pulse shortening in parametric Raman lasers with spectrally tunable zero-dispersion phase matching. We demonstrate the anti-Stokes (1168 nm) and multi-Stokes (1629 nm) picosecond pulse shortening and self-separation of single 80-ps ultra-short pulse from the zero-dispersion phase-matched parametric Raman lasers that are based on the calcite crystal without using any electro-optical device.

Abstract Lasing on the 4F3/2 → 4I13/2 secondary transition (λ = 1.34 μm) in a Nd3+ : YAG laser with phase conjugation by four-wave mixing directly in the active laser medium was experimentally studied in the regime of electro-optic Q-switching of an open multiloop cavity. The use of an electro-optic Q-switch with a controllable delay of its opening made it possible to increase the amplitude and temporal stabilities of the output laser parameters. The maximum laser pulse energy was 100 mJ at a pulse duration of 120 ns. The phase-conjugate radiation divergence was 0.8 mrad at beam quality . Nonlinear optical conversion of 1.34 μm laser radiation to visible radiation was achieved experimentally. Second and third harmonic generation at wavelengths of 0.67 and 0.446 μm with conversion efficiencies of 25 % and 8 %, respectively, was demonstrated.

Lasing on the F-4(3/2) -> I-4(13/2) secondary transition (lambda = 1.34 mu m) in a Nd3+ : YAG laser with phase conjugation by four-wave mixing directly in the active laser medium was experimentally studied in the regime of electro-optic Q-switching of an open multi-loop cavity. The use of an electro-optic Q-switch with a controllable delay of its opening made it possible to increase the amplitude and temporal stabilities of the output laser parameters. The maximum laser pulse energy was 100 mJ at a pulse duration of 120 ns. The phase-conjugate radiation divergence was 0.8 mrad at beam quality M-x(2) = M-y(2) = 1.3. Nonlinear optical conversion of 1.34 mu m laser radiation to visible radiation was achieved experimentally. Second and third harmonic generation at wavelengths of 0.67 and 0.446 mu m with conversion efficiencies of 25 % and 8 %, respectively, was demonstrated.

This article is devoted to the process of remote exposure to the radiation of fiber laser on metal shell explosive objects. The advantages of fiber lasers that allow their use in demining complexes are described. The paper presents an experimental study of the effect of fiber laser radiation profiled and non-profiled pulses on metal simulators of explosive objects. It is established that the effect of profiled pulses compared to the non-profiled allows to significantly reduce the melting time of the sheath and to decrease the required laser energy.

Lasing at a wavelength of 1.34 mu m on the F-4(3/2) -> I-4(13/2) secondary transition of Nd3+ ions in a phase-conjugate (PC) Nd3+ : YAG laser under four-wave mixing in a laser medium is theoretically and experimentally investigated. The influence of the amplified spontaneous emission at a wavelength lambda = 1.064 mu m on the parameters of phase-conjugate generation of the Nd3+ : YAG laser at lambda = 1.34 mm under passive Q switching by a V3+ : YAG crystal using two-, three-, and four-loop open cavity schemes is analysed by mathematical simulation. It is shown that there is an optimal initial transmission of a passive Q switch (PQS), the value of which decreases with increasing number of cavity feedback loops. The generation in the Nd3+ : YAG laser at lambda = 1.34 mm with an open PC multiloop cavity is experimentally obtained and studied for the first time. Emission in the form of a train of seven pulses with a total energy of 0.25 J and individual pulse energy and duration of 36 mJ and 150 ns, respectively, is obtained with an initial PQS transmission of 74%. The angular divergence of the laser beam is found to be 0.7 mrad at quality factors M-x(2) = 1.2 and M-y(2) = 1.1.

The diode-pumped Nd:SrMoO 4 self-Raman-parametric laser generation of shortened 300-ps pulse with the increased pulse energy of up to 1 μJ without any mode-locking device is experimentally demonstrated and theoretically studied.

For the first time, operation of the 1.34-μm Nd:YAG laser with an open-loop self-adaptive cavity is demonstrated. In free-running and passive Q-switching regimes output energy and temporal laser parameters were studied.

The study of the generation characteristics of Nd:YAG lasers with multiloop self-organizing phase conjugate cavities using a passive Q-switch based on a Cr:YAG crystal is carried out. It is shown that Q-switching of the phase conjugate cavity is caused not only by absorption saturation of the passive Q-switch, but also by modulation of diffraction efficiency of holographic saturable gain gratings in the Nd:YAG active laser medium.

Self-Q-switching of a loop laser cavity with a self-pumped four-wave phase-conjugate mirror in an active laser medium with the use of a Faraday isolator or a passive Q-switch is studied theoretically. It is found that, in contrast to passive Q-switching of an ordinary cavity, a passive Q-switch in a loop phase-conjugate cavity serves as an auxiliary unit that increases the self-Q-switching efficiency by gain gratings in the active laser medium, since it decreases the difference in the intensities of waves that write a phase-conjugate mirror in the active medium, which is similar to the use of a Faraday isolator. However, the passive Q-switch operates alternating the highly efficient writing of a phase-conjugate mirror in the closed state with the highly efficient generation of a giant laser pulse in the open state, which stabilizes the period of repetitive laser pulses.

In the paper we are presenting the experimental results of the blue-laser generation by nonlinear frequency conversion of Nd3+: YAG laser on the 1,34 mu m wavelength. Blue radiation at the wavelength of 0,446 mu m was realized by sum-frequency oscillation under nonlinear mixing of radiation at wavelengths of the main (1,34 mu m) and the second (0,67 mu m) harmonics in DKDP crystal. It is shown that pulse energy of the blue radiation achieved 2 mJ with pulse duration of 20 ns and conversion efficiency of 2 %.

Passive Q-switching operation of the flash-lamp pumped 1.34-μm Nd:YAG laser with loop cavity is experimentally investigated. Using a passive 47-% V:YAG Q-switch the laser generated the 380-mJ trains of 260-ns laser pulses with an individual pulse energy of 27 mJ.