Liu Yuxuan, Yang Xuezong, Zhu Chengjie, Sun Yuxiang, Li Muye, Cheng Xin, Mildren Richard P, Chen Dijun, Chen Weibiao, Feng Yan
Opt Express. 2024 May 20;32(11):18562-18571. doi: 10.1364/OE.521303.
The relative intensity noise (RIN) characteristics of a continuous-wave diamond Raman laser are investigated for the first time. The results reveal the parasitic stimulated Brillouin scattering (SBS) that usually occurred with higher-order spatial modes in the diamond Raman resonator is a pivotal factor impacting the Raman longitudinal modes and deteriorating the RIN level. The diamond Raman laser automatically switches to single-longitudinal-mode operation and the RIN level is significantly decreased in the frequency range of 200 Hz to 1 MHz after the parasitic SBS is effectively suppressed through inserting a spatial aperture or a χ nonlinear crystal into the cavity. Due to the introduction of additional nonlinear loss to the high intensity Raman fluctuations and the non-lasing spontaneous Raman modes, the χ nonlinear crystal enables better performance in the RIN-level reduction compared to the spatial aperture which can only achieve SBS inhibition. The RIN reduction routes are well suited for various crystalline Raman media to achieve high power and low intensity noise laser at different wavelengths.
首次对连续波金刚石拉曼激光器的相对强度噪声（RIN）特性进行了研究。结果表明，通常在金刚石拉曼谐振器中与高阶空间模式一起出现的寄生受激布里渊散射（SBS）是影响拉曼纵向模式并恶化RIN水平的关键因素。通过在腔内插入空间光阑或χ非线性晶体有效抑制寄生SBS后，金刚石拉曼激光器自动切换到单纵模运行，并且在200 Hz至1 MHz的频率范围内RIN水平显著降低。由于对高强度拉曼波动和非激光自发拉曼模式引入了额外的非线性损耗，与只能实现SBS抑制的空间光阑相比，χ非线性晶体在降低RIN水平方面具有更好的性能。RIN降低途径非常适合各种晶体拉曼介质，以在不同波长下实现高功率和低强度噪声激光器。
