Compact optically pumped magnetometer light source stabilization with regulated feedbacks

Abstract

Optically pumped magnetometers (OPMs) are very sensitive to magnetic field and have the advantages of portability and low cost. In the miniaturized OPM, a vertical cavity surface emitting laser (VCSEL) diode is utilized to generate the laser light for both pumping and probing, the stability of which significantly affects the sensor’s performance. Therefore, precisely control of the light source is required. This paper proposes a novel method of stabilizing the laser diode output by using a close-loop control with two feedbacks, namely: the measurement of the diode temperature and the output signal of the photodetector. The control coefficients of these two feedbacks are regulated dynamically according to the operating state of the OPM. The experimental results show that after operating for 1000 s, the Allan deviation of the photodetector signal is 3.98 ×10−4 for the proposed method, as a comparison, the Allan deviation is 2.56 ×10−2 for a conventional close-loop control technology. The proposed method performs better for long-time operations. A compact OPM is developed and tested, which employ the proposed scheme to control the output of the VCSEL diode. The experiment results show that a sensitivity of 16 fT/Hz1/2 @ 10 Hz is achieved and the OPM can operate stably in a long time.