Semi-analytical thermal analysis of high power Nd:YVO₄/KTP intracavity doubling crystal

In diode-pumped all-solid-state laser system, nonlinear optical double frequency crystal KTP, which cut at II-type phase match condition, not only oriented satisfied with fundamental light's polarization condition, but also met its half wave plate condition, and only these conditions are all fulfilled, crystal would have the maximal harmonic conversion efficiency. But double frequency crystal, which absorbed fundamental light radiation, would induce crystal interior non-uniform temperature raise, and this thermal phenomenon could cause crystal's refractive index change, and could induce thermal distortions. All these phenomena would destroy nonlinear crystal intrinsical phase matching condition, and affect output-laser's quality and double frequency conversion efficiency. To diminish this situation the key work is to obtain accurate crystal working condition's temperature distribution. KTP crystal interior temperature field is obtained by semi-analytical thermal analysis method, and all kinds of relevant parameters, which influence temperature field distribution, are analyzed. The analysis method and results have ordinary applied character. This solution can also be applied to analysis those model which have axis-symmetrical and inner heat source or other thermal models. These works play instructive effect at the optimum design of continuous wave intracavity double frequency laser system.