Coupled thermal dynamics and performance degradation in high-power continuous-wave diamond Raman lasers

Diamond is a highly promising crystalline material for high-power laser generation due to its exceptional thermal conductivity, broad optical transparency, and high nonlinear gain coefficient. However, its superior thermal conductivity also presents challenges for thermal management in laser systems. In this study, the thermal evolution of a diamond crystal and its impact on the output performance of a continuous-wave (CW) diamond Raman laser were experimentally investigated using real-time infrared thermography. The results reveal that, once the pump power exceeds the lasing threshold and Stokes radiation is initiated, the surface temperature of the diamond rises rapidly and exhibits significant spatial non-uniformity, with peak temperatures concentrated at the center of the pump beam. The Stokes output power exhibits a nonlinear “rise-and-fall” trend with increasing pump power due to thermal lensing–induced cavity mode mismatch. Combined theoretical modeling and experimental validation reveal a coupled relationship among the crystal temperature, thermal lens focal length, and Stokes beam characteristics. The analysis demonstrates that temperature is not an independent parameter; instead, it acts as a coupled variable co-evolving with pump power, jointly influencing Raman gain and cavity mode stability. These findings provide both theoretical insight and experimental evidence to support the optimization of thermal management strategies in high-power diamond Raman lasers. To the best of our knowledge, this is the first study to systematically reveal the nonlinear coupling among temperature evolution, thermal lensing, and output power degradation under CW operation, providing new insights for the design of thermally robust Raman laser systems.