| OPO is an important component of laser frequency conversion technology with wide frequency conversion range and high energy conversion efficiency.OPO technology can flexibly combine with other lasers to form a laser system with different performance.High power tunable pulsed light source produced by OPO has important applications in spectral detection.Q-Switched Nd:YAG laser is a typical high power pulse light sources which widely used in various applications.And its frequency doubling in 532 nm is a common pump source for tunable laser.The purpose of this paper is to produce wavelength tunable pulse in the near infrared band by combinating the OPO and Nd: YAG frequency doubling laser.The main contents of this paper are as follows: 1.The theory of nonlinear optics and crystal physics is introduced.The critical phase-matching angle to converting the 532 nm to 800 nm in BBO,LBO,Bi BO and KTP crystal through the Sellmeier dispersion equation and corresponding effective nonlinear coefficient is calculated.The final choice of the OPO system is LBO crystal in the XY plane with type I phase match.2.How the pump light and OPO cavity parameters changes the threshold and conversion efficiency of OPO is analysed and the methods to improve the energy conversion efficiency is given.The two kinds of OPO modes such as pump enhanced OPO and non-pump enhanced OPO are studied experimentally.By optimizing the reflectance of the resonant cavity mirror,up to 30% of the energy conversion is obtained in the pump enhanced OPO system.3.The parameters of OPO temperature control system are given based on the calculation of the temperature influenced wavelength and gain spectrum of OPO according to the crystal's thermal optical dispersion equation.Finally,the near-infrared band output through 760 nm to 790 nm is obtained by temperature tuning and the influence of the angle error between the crystal and the pump light on the temperature tuning range of OPO is analyzed. |
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