Coupled effects of cavity photon lifetime, oscillation threshold, and group-velocity mismatch on pulse width...

This manuscript presents the critical resonator length as a key parameter and develops a multiphysics coupling model to systematically analyze the combined effects of cavity photon lifetime, oscillation threshold, and group-velocity mismatch (GVM) on pulse width evolution in a single resonator optical parametric oscillator (OPO) system. By constructing this model and performing experiments that vary the resonator length, the study demonstrates how these physical effects interact over a specific range of resonator lengths, influencing the pulse width evolution of both signal and idler beams. In the short-cavity region (resonator length below the critical value L_critical), the signal pulse width is primarily governed by the cavity photon lifetime effect and remains stable. In the long-cavity region (resonator length exceeding the critical value L_critical), the combined effects of the oscillation threshold and GVM lead to pulse width compression, which eventually stabilizes. The idler pulse width is predominantly influenced by the GVM effect, showing a decreasing trend that ultimately reaches saturation. Experimental data are consistent with numerical simulations, confirming the validity of the multiphysics coupling model and providing a theoretical basis for optimizing OPO system design.