Optical Parametric Oscillator Pumped By Dual-Wavelength Cascaded Raman Wave

Dual-wavelength lasers have a very important role in holographic interferometry,differential absorption radar,and difference frequency generation terahertz sources.In this paper,we proposed a Mg O:PPLN-OPO pumped by a dual-wavelength cascaded Raman laser to realize the dual-wavelength signal wave tunable output.The cascaded characteristics of stimulated Raman scattering and its beam self-cleaning effect were studied,and the cascaded dual-wavelength Nd:YVO₄/YVO₄ Raman laser was optimized separately by using the composite cavity structure to achieve stable output;it is used as the pump source to achieve a tunable output of dual-wavelength signal wave Mg O:PPLN-OPO pumped by the cascaded dual-wavelength Raman wave external cavity,as follows:1.The rate equation of the actively Q-switched first-order Raman laser was established,and the second-order Raman scattering term is added to obtain the rate equation of the dual-wavelength cascaded Raman laser for simulation.By analyze the dynamic process of intracavity photon conversion,the equilibrium mechanism of intracavity stimulated radiation and stimulated Raman scattering was obtained.Thereby,we can provide a resonant cavity parameter optimization scheme.2.The experimental study of the first-order Raman laser at 1176 nm and the dual-wavelength cascaded Raman laser at 1176 nm and 1313 nm was carried out to investigate the cascaded gain characteristics of the dual-wavelength cascaded Raman laser by replacing the coupling output mirrors with different transmittance.At the output coupling mirror transmittance of 1176 nm T=25%and 1313 nm T=80%,2.51W 1176 nm first-order Raman wave and 1.52 W 1313 nm second-order Raman wave were obtained,and the total conversion efficiency was 14%.The clean-up effect of the solid-state cascaded Raman laser was also studied experimentally.3.The Mg O:PPLN-OPO tuning curve was simulated and the period of the PPLN crystal used was designed to achieve a tunable dual-wavelength output with a large output wavelength interval and a similar output wavelength in combination with temperature tuning.A theoretical analysis of the linewidth spreading characteristics of Mg O:PPLN-OPO and numerical simulations were carried out to provide guidance for the subsequent experiments.4.An experimental study of the 1176 nm and 1313 nm cascaded dual-wavelength Raman lasers pumped with Mg O:PPLN-OPO in the external cavity was carried out,and the signal wave pumped by 1176 nm（1550-2212 nm）and 1313 nm（1768-2182 nm）were achieved at crystal polarization periods of 27.6,29.1,31.4,32.1 and 34.4μm.The dual-wavelength signal wave was tunable,the dual-wavelength signal wave with a wavelength interval of 220 nm and the similar dual-wavelength signal wave with a wavelength near 2.2μm were obtained.At the period of 34.4μm,the conversion efficiency of Raman wave to dual-wavelength signal light was 34.2%when the incident Raman power was 2.61 W.The output power is 1.02 W when the maximum incident Raman power was 3.33 W.