Theory analysis of 2m laser output based on PPLN

In order to generate 2m laser,a novel method was adopted with periodically poled lithium niobate(PPLN) as a nonlinear crystal in optical parametric oscillator(OPO).From the Sellmeier function of PPLN,given the momentum conservation and energy conservation,series of theoretical analysis and numerical calculation are conducted.Firstly,it was obtained that the polarization period of PPLN was 31.35m at 120℃ Then the curves of the relations between the wavelength and polarization period,between the wavelength and the incident angle were drawn.Finally,starting from the phase synchronization factor sinc2(Kl/2),the allowance angle,allowance polarization period and allowance temperature were calculated.This method not only can overcome walk-off effect of birefringence and dispersion,but also make full use of the maximum effective nonlinear coefficient of the crystals,so the efficiency of the conversion can be increased.These theoretical results provide the foundation for the future experimental study about PPLN-quasi-phase matching-OPOs.