Frequency stabilization of dual-mode microchip laser by means of beat frequency stabilization

The stabilization of the laser oscillation frequency of a dual-mode microchip laser was demonstrated by stabilizing the beat frequency generated by the two simultaneously oscillating longitudinal modes. In the experiment, a beat frequency of 101 GHz was stabilized to +/- 50 kHz using negative feedback control. As a result, the fluctuation of the laser oscillation frequency was finally stabilized to +/- 50 MHz or less within the resolution of the measurement instrument with an estimated short-term fluctuation of +/- 3.3 MHz. Furthermore, using this technique, the initial drift of the laser oscillation frequency was significantly reduced, and the linear sweep operation of the laser oscillation frequency was successfully demonstrated by linearly sweeping the beat frequency over 30 MHz while maintaining locking. Our technique is essentially robust and suitable for the miniaturization of the system in the future.