Stable semiconductor laser with a 7-Hz linewidth by an optical-electrical double-feedback technique.

A semiconductor laser with a linewidth of 7 Hz locking to a supercavity was achieved by using an optical-electrical double-feedback technique. The emitted power concentration within the stabilized field spectrum was 81%. The minimum value of the square root of the Allan variance for the frequency stability was 2.4 x 10(-14) at the integration time of 70 msec.