High-power continuous-wave fiber-pumped Ti:sapphire laser based on a thermally insensitive resonator design

In ultra-sensitive weak magnetic field and inertial measurement systems based on spin-exchange relaxation-free (SERF) technology, continuous-wave (CW) Ti:sapphire lasers are required to deliver high output power, excellent frequency stability, and long-term power stability to ensure high magnetic field sensitivity. However, under high-power pumping, thermal effects in the gain medium significantly reduce the resonator's stability region, thereby degrading the long-term power stability of the laser output. To address this challenge, a 37 W, 532 nm fiber laser was employed as the pump source, and a thermally insensitive four-mirror ring cavity was designed. Under this configuration, the laser system achieved 6.36 W of continuous single-frequency output at 780 nm, surpassing previously reported power levels for fiber-pumped Ti:sapphire lasers. A 15-hour power stability test conducted at 770 nm yielded an average output of 5.666 W, with a root mean square (RMS) fluctuation of 0.367 % and a peak-to-peak variation of 1.78 %. These results confirm the effectiveness of the thermally robust cavity design in enhancing power stability and demonstrate the system's suitability for high-precision magnetic field measurements. Furthermore, comprehensive characterizations of intensity noise, longitudinal mode structure, beam quality, and wavelength tunability were performed. The results indicate that the laser system meets the performance requirements for precision measurement applications and exhibits excellent overall characteristics.