Adaptive thermal power stabilization-based ultra-low-frequency intensity noise suppression in a MOPA fiber laser system.

The importance of ultra-low-frequency (<1 Hz) intensity noise in laser systems has been widely recognized for improving the performance of spin-exchange relaxation-free (SERF) atomic devices. The elevated intensity noise observed in frequency-doubled light has been directly linked to ultra-low-frequency fluctuations in the fundamental laser output, underscoring the need for effective suppression strategies in master oscillator power amplifier (MOPA) systems. In this work, a temperature-dependent simulation model of a MOPA system was developed to theoretically analyze the influence of thermal effects on the amplification process. Simulations revealed a complex and nonlinear relationship between temperature variations and output power. To confirm the theoretical findings, a high-precision temperature control system was constructed, and the significant impact of thermal fluctuations on output power was experimentally verified. An adaptive temperature control strategy was subsequently proposed, in which real-time feedback from the output power signal was combined with ambient temperature measurements to adjust control parameters dynamically. Through this approach, a 30% improvement in power stability was achieved, with a peak-to-peak (P-P) fluctuation of 0.757% and a root mean square (RMS) error of 0.15%. Furthermore, effective suppression of ultra-low-frequency intensity noise was demonstrated using the adaptive thermal control method, with up to a 5 dB reduction observed in the 0.001-1 Hz range. This study provides what we believe to be the first experimental validation of power stabilization and ultra-low-frequency intensity noise suppression in a fiber MOPA system through temperature control. A practical and generalizable solution has been presented for achieving high-stability, low-noise laser sources suitable for SERF-based inertial sensing applications.