Spectrum tuning and stabling of a mid-infrared singly resonant optical parametric oscillator using intracavity etalon: theoretical and experimental investigation

In the present work, the effects of an intracavity etalon inside a singly resonant optical parametric oscillator (SRO-OPO) resonator on the power and spectrum stability and tuning characteristics of the signal and idler waves has been theoretically modeled. Real experimental parameters associated with a laboratory SRO-OPO are used to compute the spectral bandwidth of oscillating signal through calculation of the nonlinear coupled equations while the input pump power is assumed to be adjusted at several multiples of oscillation thresholds for sets of thickness-variable slab glass etalon. Simulation results show by using thicker etalons a significant reduction of similar to 60 times in the signal bandwidth can be obtained at higher levels of the SRO-OPO threshold which resulted in the more stability of the outcoupled waves. The simulated results have been realized by using a slab glass of etalon inside the cavity of a PPLN-base SRO-OPO setup constructed in the laboratory. It is found that the peak-to-peak fluctuations of both signal and idler waves reduces to less than similar to 0.05% whereas the thickness of the internal etalon is increased to similar to 1.1 mm and the device is adjusted to operate around the threshold. This reflects good consistency between experimental measurements and theoretical model. Finally, more than similar to +/- 15 nm tuning of the SRO-OPO output is also performed by rotating the intracavity over similar to +/- 5 degrees.