VCSEL frequency stabilization for optically pumped magnetometers

Optically pumped magnetometers (OPMs) have developed rapidly in the bio-magnetic measurement field, which requires lasers with stable frequency and intensity for high sensitivity. Herein we stabilize a vertical-cavity surface-emitting laser (VCSEL) without any additional setup except for the parts of an OPM. The linewidth of the absorption spectrum as a frequency reference is broadened to 40 GHz owing to pressure broadening. To enhance performance, the VCSEL injection current and temperature are tuned simultaneously using a closed-loop control system. The experiments reveal that the VCSEL frequency stability achieves 2×10-7 at an average time of 1 s, and the intensity noise is 1×10-6 V/Hz1/2 at 1–100 Hz. This approach is useful for suppressing OPM noise without additional sensor probe parts.