Piston error characteristics of the self-phase-controlled stimulated Brillouin scattering phase conjugate mirrors

It was reported by Kong et al. that the self-phase-controlled stimulated Brillouin scattering phase conjugate mirror (SBS-PCM) is useful for the beam combination laser amplifier system, which generally introduces a phase delay (piston error) between combined beams along separate optical paths. In this work, we have investigated the piston error characteristics of two schemes for self-phase-controlled SBS-PCMs, a collinear scheme and a triangular scheme. Experimental results show that the piston errors of the reflected beams are 2kδ2kδ and kδkδ for the former and the latter scheme, respectively, where k is the wave number and δ is the optical path difference (OPD) variation introduced into the pass.