Wavelength Locking of Vertical-Cavity Surface-Emitting Laser in Optically Pumped Magnetometer

Aimed at the requirements of optically pumped magnetometer (OPM) for miniaturization, low power consumption and laser frequency stability, a wavelength locking control scheme for vertical-cavity surface-emitting laser is proposed. The proposed method of laser wavelength locking based on Doppler absorption optical feedback takes the wavelength of D1 line Fg = 4→Fe = 3 transition in 133Cs atom as the reference. The atom vapor cell in OPM is also used as the working cell for wavelength locking so that the laser wavelength can be locked on the corresponding wavelength of the D1 line transition without any additional setup. The digital proportional integral differential and fuzzy control algorithm is used for laser temperature control and the temperature fluctuation is within ±0.005 ℃. Laser current driving is realized based on current mirror and the current fluctuation is within ±50 nA, which provides a good hardware foundation for laser wavelength locking. Finally, a stable signal output of the OPM for up to two hours under laboratory conditions is realized.