ISSN 1060-992X, Optical Memory and Neural Networks (Information Optics), 2013, Vol. 22, No. 4, pp. 1–5. © Allerton Press, Inc., 2013. 1 INTRODUCTION Phase conjugate laser operation is very important for aim of transfer of power for large, in particular space, distances, and also remote action on several subjects. The phase conjugation (PC) effect allows not only realizing a self-compensation of distortions of a propagating laser radiation, but also solving a prob- lem of high-efficiency and high-power laser generation with good beam quality close to diffraction limit. One of the ways to implement phase conjugate laser generation is to realize self-pumped degenerate four-wave mixing directly in the laser medium [1–11]. Any additional PC elements or PC pumping sources are not required for such self-pumping phase-conjugate (self-PC) technique. The self-PC laser cavity has a loop configuration with self-intersection of intracavity beams in the laser medium. In real-time operation mode these intersected beams interfere and write holographic gratings as spatial modulation of laser gain. Diffraction of the laser radiation on these gain gratings occurs with PC and gives a feedback for the self-PC laser generation. The self-PC laser generation starts when a round-trip gain of the laser cavity becomes more than unity that is provided by not only amplification of the laser radiation propagating inside the loop cavity, but also efficient diffraction of this radiation on gain grating. So the laser gain should be high enough due to multifunctional operation of the laser medium. In [3–5, 10, 11] to solve this problem the additional laser amplifiers in the intracavity loop were used. Realization of many self- intersections with writing of many gain gratings in the single laser element is an alternative method increasing the round-trip gain of the self-PC laser loop cavity [10]. Use of high efficient pumping of the laser medium by high-intensity laser diodes is one more method of increasing the laser gain that allows to realize the self-PC laser generation [4, 6, 7, 9–11]. All-Solid-State Nd:YAG Lasers with Self-Pumped Multiwave-Mixing Phase Conjugate Cavities A. P. Pogoda a, b , *, V. F. Lebedev a, b , P. S. Makarchuk b , S. N. Smetanin c , and A. S. Boreysho a, b a Laser Systems LTD, Saint Petersburg, Russia b Baltic State Technical University “VOENMEKH”, Saint Petersburg, Russia c Kovrov State Technological Academy, Vladimir region, Russia e-mail : Pogoda@lsystems.ru Received August 20, 2013 Abstract—Several configurations of the laser self-pumped phase-conjugate cavities with multiwave mixing directly in the laser medium based on a single Nd:YAG laser element pumped by multikilowatt laser diode 2D stacks are experimentally studied and compared. In the laser configurations with six- and eight-wave mixing there are generated a high-intensive self-Q-switched 200-ns laser pulse fol- lowed by low-intensive free-running lasing. An increase of the number of waves taking part in multi- wave mixing from six to eight leads to increase in the laser maximum output energy and optical-to- optical efficiency from 0.55 J up to 1.1 J and from 8.3% up to 18% respectively. In the laser configura- tion with ten-wave mixing the energy characteristic is similar to the same in the laser configuration with eight-wave mixing, but the temporal and spectral characteristics are different from the same in the laser configurations with six- and eight-wave mixing. In last laser configuration not only the first pulse, but also all the train of pulses is generated in high-intensive TEM 00 diffraction-limited (M 2 = 1.3–1.5) single-frequency self-Q-switched mode via writing and erasing the gain gratings by the int- racavity radiation. Keywords: Solid-state lasers, self-pumped phase-conjugate laser, multiloop configuration, multi-wave mixing DOI: 10.3103/S1060992X13040115