Investigation of Intensity Noise Characteristics in Continuous‐Wave Ti: Sapphire Lasers Pumped by 532 nm Fiber Lasers

Abstract Continuous‐wave single‐frequency Ti: sapphire lasers, with their widely tunable wavelength range, are being increasingly used as optical pumping sources for alkali metal atoms in quantum precision measurements, where low‐intensity noise is critical. In this work, A quantum noise theory model is applied to characterize the noise dynamics of a fiber‐laser‐pumped ring cavity Ti: sapphire laser system. The influences of output coupler transmittance, intracavity loss, and cavity length on intensity noise are theoretically analyzed. Experiments are conducted to measure the pump noise contribution, investigate the effects of pump polarization, intracavity isolator loss, output wavelength, crystal cooling surface temperatures, and cavity length within the stability zone. The results confirmed that low‐frequency noise below the resonant relaxation oscillation (RRO) predominantly originated from the pump source, and cavity loss is the main factor influencing the RRO peak. Active stabilization loops, using an acousto‐optic modulator (AOM) for power control and PDH locking for frequency stabilization, are implemented and effectively suppress low‐frequency (10–100 Hz) intensity noise and (1–100 Hz) phase noise. This work provided a practical approach for noise optimization and significantly enhanced the application prospects of Ti: sapphire lasers in quantum precision measurements.