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报道了一种可用于产生窄带太赫兹(THz)波的超大频差双纵模Nd…YVO4激光器。该激光器基于薄片激光介质和微型腔来实现连续双纵模运转,两个纵模间的频差处于THz波段,通过调节激光器的腔长可实现频差在0.1～0.2THz范围内的调谐;单个纵模的谱线宽度仅为20MHz;激光束空间分布为单横模,光束质量M2因子为1.292;在630mW抽运光下,输出连续激光功率为116mW,斜率效率为18.53%,线偏振度为0.993。该激光器输出的双频光可被用作种子光经放大后来获得高功率THz差频抽运光,再在非线性晶体中通过共线差频就能实现窄带THz波辐射,理论分析表明THz波辐射谱线宽度约为THz差频抽运光的槡2倍,另外采用光斑半径为50μm和峰值功率在千瓦量级的THz差频抽运光,在0.8mm厚DAST晶体中可得到毫瓦量级的THz波输出。
A super-frequency-shifted dual-mode Nd: YVO4 laser that can be used to generate narrow-band THz waves is reported. The laser is based on lamellar laser medium and micro cavity to realize continuous dual longitudinal mode operation. The frequency difference between the two longitudinal modes is in the THz band. By adjusting the cavity length of the laser, the frequency difference can be tuned in the range of 0.1-0.2 THz. The spectral width of longitudinal mode is only 20MHz. The spatial distribution of laser beam is single transverse mode, the beam quality factor is 1.292. Under 630mW pumping light, the output continuous laser power is 116mW, the slope efficiency is 18.53% 0.993. The dual-frequency light output by the laser can be used as seed light to amplify to obtain high-power THz difference frequency pumping light, and then the narrow-band THz wave radiation can be achieved through the collinear difference frequency in the nonlinear crystal. The theoretical analysis shows that the THz wave The radiation line width is about 槡 2 times the THz difference frequency pumping light. In addition, a THz difference frequency pumping light having a spot radius of 50 μm and a peak power of the order of kilowatts is used, and a milliwatt amount is obtained in a 0.8 mm thick DAST crystal THz wave output level.