The phase locking control of the multichannel holographic neodymium laser system with the help of a passive Q-switch

Abstract

The phase locking of laser generators requires compensation of the distortions of laser emission and thedifference in the lengths of resonators. In [1–3], wesuggested to phase the diffractioncoupled loop laserresonators [4, 5] that provide the selfcompensation ofthe lengths and optical distortions with the phase configuration (PC) on the holographic gain gratings andexperimentally produced the phased twochannel andthreechannel holographic YAG : Nd laser systemswith longrange and shortrange coupling. The lasersystem with longrange coupling (each channel witheach one) provides a high interference contrast ofemission of laser channels up to 0.9 [2]. However, ithas limitations for an increase in the number of laserchannels because of their optical coupling in one common active element. On the contrary, in the schemewith shortrange coupling (coupling of neighboringchannels), unlimited scaling of the number of laserchannels can be realized since each pair of neighboring channels has its own coupling active element.However, the interference contrast of the twochannelYAG : Nd laser system operating by such scheme in afree running mode was no higher than 0.6 [3].In this work, for the phase locking control of a multichannel holographic laser system with shortrangecoupling, we suggest using a passive Qswitch (PQS)mounted in one of the laser channels.We suggest new schemes of multichannel laser systems shown in Fig. 1. The passive Qswitch is mountednear the intersection of laser beams of one of the laserchannels (Fig. 1a) or a pair of laser channels (Figs. 1b,1c). The reason is that the passive Qswitch (PQS) ofloop laser resonators is performed only in such cases[4, 5]. Figures 1b and 1c show the schemes with anunlimited number of parallel coupled laser channels(phased laser linear array). The last scheme (Fig. 1c)shows the possibility of scaling (by a factor of 2, but it isalso possibly larger) of the number of sequentially connected active elements (AE) inside each channel withthe use of the AEs with low gain factors, for example,during generation of the neodymium laser at a wavelength of about 1.3 μm, while mounting additionalsweep mirrors between the AEs inside the laser channel provides introduction of selective reflection lossesfor the wavelength of 1.06 μm. In this case, forgeneration at a wavelength of 1.06 μm, theLiF : or YAG : Cr