Optical characterization of a vertical cavity surface emitting laser for a coherent population trapping frequency reference

Characterization of a vertical cavity surface emitting laser source for a frequency reference that uses coherent population trapping with atomic rubidium is reported. The frequency reference requires a low-noise laser that operates in a single transverse mode at 794.7nm. We show that biasing the laser at low output power and modulating it at higher frequency than its low relaxation oscillation frequency are necessary to obtain symmetric modulation sidebands and improve the long-term performance of the frequency reference.