Second-harmonic generation at 1560 nm using a KNbO/sub 3/ crystal in a resonant ring cavity for frequency-locking to a rubidium D/sub 2/-line component

The second harmonic of a 1560 nm DFB laser is generated in a KNbO/sub 3/ crystal placed in a resonant ring resonator. The laser is frequency stabilized using the optical feedback from the counterpropagating mode of the cavity. A second-harmonic signal of 0.38 /spl mu/W is produced and used to observe the /sup 87/Rb absorption profile.