Experimental study of parametric-diffraction suppression via idler dissipation for multi-beam-pumped optical parametric amplification

Abstract

Multi-beam-pumped optical parametric chirped-pulse amplification (OPCPA) systems suffer from parasitic parametric diffraction caused by nonlinear cross-coupling among intense laser beams, which severely degrades conversion efficiency. Although quasi-parametric amplification has been proposed to suppress cascaded nonlinear effects, its quantitative effectiveness in mitigating multi-beam parametric diffraction has remained experimentally unexplored. In this work, we experimentally demonstrate a quasi-parametric chirped-pulse amplification (QPCPA) scheme that actively depletes idler waves in a Sm-doped yttrium calcium oxyborate crystal to suppress parametric diffraction. We characterize the dependence of parametric diffraction on the pump beam angle and intensity, and evaluate the suppression performance provided by idler dissipation. Experimental results in a two-beam-pumped configuration show that the QPCPA scheme reduces pump-to-diffraction conversion by more than 60% compared to conventional OPCPA. Robust cross-coupling suppression is maintained across a range of operating conditions. By establishing a clear experimental link between idler dissipation and diffraction suppression, this work provides a practical pathway for scalable energy enhancement in multi-beam nonlinear combining systems, supporting the advancement of high-energy OPCPA architectures.