Fiber laser-pumped Ti:sapphire laser with ultra-low-intensity noise and frequency stabilization for quantum precision measurement applications

We developed a fiber-laser-pumped Ti:sapphire laser system designed for quantum precision measurement applications. By employing a 35 W single-frequency 532 nm fiber laser as the pump source, the system delivered continuous-wave output powers of 4.12 W at 770.108 nm (D₁ line, K), 4.72 W at 780.244 nm (D₂ line, Rb), and 5.29 W at 794.982 nm (D₁ line, Rb), thereby fulfilling the requirements for optical pumping and probing of alkali atoms. To enhance frequency stability, saturated absorption spectroscopy was used to lock the laser frequency, resulting in frequency drifts below 1 MHz over two hours. Furthermore, since low-frequency intensity noise (DC-100 Hz) critically affects spin-relaxation-free quantum sensing, we carried out a theoretical analysis which identified the pump laser as the dominant noise source. By implementing feedback control to the pump source as well as an external noise suppression, both methods achieved over 30 dB of intensity noise suppression within the DC-4kHz frequency range. In addition, improved beam pointing stability further reduced noise below 3 Hz. These results collectively demonstrate the system's strong potential for quantum sensing applications.