为了避免阳光背景干扰, 针对XeF(C-A)蓝绿激光水下应用需求开展了激光线宽压缩实验以提高信噪比。采用内置标准具的光栅谐振腔开展相关实验。利用光栅腔实现亚纳米级的激光线宽输出, 然后在此基础上, 通过插入标准具进行更精细的激光线宽压缩实验。利用光栅腔, 采用1 200线/mm光栅并提高光栅辐照面积可以实现0.14 nm的激光线宽输出。腔内插入反射率为50%的标准具, 可以进一步将激光线宽压缩至39 pm, 激光单脉冲能量约为65 mJ, 脉冲宽度为1 μs。实验结果表明: 尽管XeF(C-A)蓝绿激光器的增益系数较低, 但是通过优化光栅和标准具的工作参数, 对谐振腔光学损耗进行合理的控制, 激光器可以实现10 pm量级的激光线宽输出。

In order to improve the signal-to-noise ratio for laser applications underwater, a grating resonator with an intra-cavity etalon was designed to compress the spectrum of XeF blue-green laser. First, a grating resonator was used to obtain a sub-nanometer laser linewidth, and then, a further spectral compression was performed by inserting an etalon into the grating resonator. The experimental results show that a linewidth of 0.14 nm can be obtained by using a 1 200 line/mm grating, and the linewidth can be further compressed to 39 pm by inserting an etalon, with a reflectivity of 50%, in the grating resonator. The final laser pulse energy is about 65 mJ and the pulse duration is 1 μs. Although the gain coefficient of the XeF (C-A) laser is low, the optical loss of the resonator can be reasonably controlled by optimizing the working parameters of the grating and the etalon, thereby a 10pm-level laser linewidth can be realized.