增益介质位置对腔外倍频效率的影响

The effect of the gain medium position in the resonator on the external second harmonic generation (SHG) conversion efficiency was studied. A MgO-doped periodically poled LiNbO ₃ crystal (MgO:PPLN) was utilized to achieve a 532-nm green-light laser outside the resonator of a mode-locked diode-pumped Nd:YVO ₄ 1064-nm laser. We theoretically and experimentally verified that increasing the mirror/crystal separation could reduce the longitudinal mode number, narrow the linewidth and stabilize the mode locked pulse owing to the spatial burning hole effect. These phenomena would further affect the SHG conversion efficiency.The experimental results show that, increasing the mirror/crystal separation could promote the SHG conversion efficiency with the fixed focus length, especially at the higher pump power. The theoretical analysis and experimental results have reference significance for improving the SHG efficiency of the external end-pumped mode-locked laser.