High-power single-mode master oscillator power amplifier system at 795  nm for a 128-channel SERF magnetometer

Emerging quantum sensing applications require semiconductor lasers with single-mode and low-divergence characteristics at typical atomic pumping wavelengths. However, conventional distributed feedback (DFB) lasers of this kind are limited by low power output, which is a major drawback for current high-precision quantum sensing systems. In this study, a high-performance master oscillator power amplifier (MOPA) is developed, achieving a continuous-wave (CW) output of 2.8 W at 300 K around 795 nm. The fluctuation of power output is reduced from 4.3% to 1.2% compared with conventional systems by the implementation of specially designed power supply feedback. After the optimization of noise performance by coating, TA simultaneously obtains considerable beam quality, signal-to-noise ratio (SNR), and output power. The amplifier spontaneous emission (ASE) noise is proven as the primary cause for the degradation of both longitudinal and transverse modes. The side-mode suppression ratio (SMSR) of the system is enhanced to 64.13 dB by incorporating a narrowband filter. The assembled MOPA system achieves an average sensitivity of 9.51fT/Hz^1/2 across 128 channels in spin-exchange relaxation free (SERF) magnetometer operation, paving the way for extensive deployment in molecular sensing and medical diagnosis.