2.1 W连续绿光输出的一阶准相位匹配内腔倍频

利用周期极化化学计量比掺氧化镁LiTaO3晶体(PP-MgO∶SLT),对半导体激光器(LD)端面抽运的1064-nm-Nd∶YVO4激光器进行了一阶准相位匹配(QPM)内腔倍频(ISHG)。PP-MgO∶SLT晶体长20 mm,极化周期为7.93μm(室温下),利用外加电场极化法制作,极化沿晶体的z向进行。实验中基频光波和倍频光波均沿晶体z向偏振以利用其最大的有效非线性系数。Nd∶YVO4激光器选用三镜折叠腔结构,在半导体激光器抽运功率为11 W,晶体温度为70.4℃时,产生了最大输出功率为2.1 W的连续绿光激光,光-光转换效率为19%。同时对PP-MgO∶SLT晶体外腔单程倍频下的转换效率与晶体温度间的关系进行了理论研究。实验中测得的内腔倍频的允许温度要远大于外腔单程倍频;另外,观察到随着晶体温度的变化倍频光功率出现突然下降的现象,并给出了相应的讨论。

2.1 W Continuous Wave Green Light Output by First-Order Quasi-Phase-Matched Intracavity Second Harmonic Generation

First-order quasi-phase-matched intracavity second harmonic generation (ISHG) internal to a 1064-nm-Nd∶YVO4 laser end-pumped by a laser diode (LD) based on MgO-doped stoichiometric periodically poled lithium tantalate (PP-MgO∶SLT) is demonstrated. The PP-MgO∶SLT crystal is 20-mm-long and has a grating period of 7.93 μm (at room temperature), which is periodically poled along the z-axis by using the external electric poling technique. The fundamental and second harmonic waves are of z-polarization to access the largest effective nonlinear coefficient. Using a three-mirror folded cavity design for the Nd∶YVO4 laser, the maximum green light output power of 2.1 W and the conversion efficiency of 19% are achieved at an incident LD pump power of 11 W. The relationship between the conversion efficiency of a single-pass extracavity second harmonic generation (ESHG) in PP-MgO∶SLT and the crystal temperature is theoretically investigated. It is found that the measured acceptance temperature bandwidth of the ISHG is significantly wider than that of the ESHG. In addition, the ISHG curve shows an abrupt decrease in second harmonic power as a function of the crystal temperature, and the corresponding discussion is presented.