Generation of a single-frequency 509 nm laser with over 80% efficiency and 7 W power using an optimized external ring...

An improved computational method is proposed to optimize the transmission of the input-coupling mirror in an external ring cavity incorporating a MgO-doped periodically-poled stoichiometric LiTaO₃ (MgO:PPSLT) crystal, thereby enhancing the second harmonic generation process. This approach facilitates the generation of a continuous-wave single-frequency green laser at 509 nm with improved performance, achieving an output power of 7.15 W and a conversion efficiency of 83.4%. Utilizing the Pound-Drever-Hall locking technique, the frequency doubler remains stably locked with a root mean square power instability of ±0.12% within one hour. To the best of our knowledge, this is the first reported demonstration that simultaneously achieves an output power exceeding 7 W, a conversion efficiency above 80%, and high stability in a continuous-wave frequency-doubled green laser system with an output wavelength below 532 nm. This system is promising for applications in cesium Rydberg atom studies and as a pump source for Ti:sapphire lasers.