Multichannel laser system with phase conjugation and interchannel phase locking by laser gain hologram

Abstract

The development of high-brightness laser array with the phase locking of many laser channels is one of the topical problems that opens up prospects for a significant increase of the output energy characteristics and the creation of composite laser aperture with high directivity and brightness. In this case, a decrease in the radiation exposure of the laser optical elements leads to an increase in their lifetime. The principles for the construction of multichannel laser systems based on the short or long-range coupling between the lasers and the injection of the reference signal for the phase locking of the controlled laser channels can be found in [1].Althought the possibility for the phase locking of solid-state lasers is limited due to significant dynamic optical distortions of the active media at high-power pumping the phase-conjugated lasers are promising for phase locking due to real-time self-compensation of the distortions.Recently, we demonstrated [2] a two-and three-channel holographic Nd:YAG laser system with a parallel coupling between self-phase-conjugate loop laser oscillators. The principal possibility of self-phase locking of these oscillators by four-wave mixing on gain grating written directly in the active laser medium was demonstrated.In this report, a phase-locked lasing of the multichannel holographic Nd:YAG laser system based on self-phase-conjugate loop oscillators is theoretically treated and experimentally demonstrated in accordance withthe transient numerical modeling that provided insight into the temporal dynamics of the phase-locked multichannel holographic lasers. For different architecture of the multichannel laser system the oscillation dynamics and phase-locking conditions at a variation of the laser-channel gain mismatch are considered.A theoretical model of interaction of four and six single-mode beams with an active laser medium was developed in order to describe the oscillation dynamics and phase-locking conditions of the multichannel holographic laser system with different architecture having long-range andshort-range holographic coupling. We assumed that in each channel its own mode is presented and a part of radiation is injected from one channelto another with the help of holographic gain grating recorded directly in the activelaser medium.~~~~~~~Fig. 1. CCD image of interference pattern the active laser medium.Conditions of the highest contrast realization for an interference pattern of output beams of the multichannel laser system are determined. Fig. 1 demonstrates a typical interference pattern of three phase-locked self-Q-switched laser beams with an energy of 0.35 J and a pulse duration of 60 ns experimentally realized by us. Qualitatively different lasing regimes of the phase-locked three-channel Nd:YAG laser system with the contrast of the interference pattern of the output beams ranging from 0.55 to 0.9 are studied. The experimental results obtained are generalized to multichannel holographic laser systems with more than three channels. So a self-injection regime ...