Experimental and dynamical study of a dual Q-switched intracavity OPO based on few-layer MoSe₂ SA

A 2.5nm-thickness molybdenum diselenide (MoSe₂) saturable absorber (SA) is prepared by electron beam evaporation (EBE) method. Applying the prepared MoSe₂ SA to an acousto-optic (AO) Q-switched fundamental laser, a dual-loss-modulated intra-cavity optical parametric oscillator (IOPO) has been experimentally realized. The signal-pulse train from this IOPO has 0.0053 standard deviation (SD) of pulse amplitude. When the MoSe₂ SA is applied to IOPO, the signal pulse is compressed by maximum 68%, the peak power increases by 274%, and the nonlinear conversion increases by 12.6%. To solve the established rate equation of IOPO, the ground-state and excited-state absorption cross section of MoSe₂ are rationally estimated to be 1.04×10^-18cm^-2 and 6.25×10^-19cm^-2 from the measured transmittance curve, and the excited-state lifetime is 275.6µs. The numerical solution of the equations fits the experimental data well.