All-optical frequency stabilization and linewidth reduction of distributed feedback diode lasers by polarization rotated optical feedback.

The frequency of a distributed feedback diode laser (DFB-LD) is stabilized on Cesium ((133)Cs) D(2) saturated absorption lines by the polarization rotated optical feedback method (PROF). Different from the conventional frequency stabilization methods by adjusting the LD pump current, no extra electrical feedback is needed with the PROF. The self-homodyne beat spectra FWHM linewidth of the DFB laser is measured to be 1.1 MHz, greatly reduced by a factor of about 40 from its free-running linewidth of 44 MHz; and the optical frequency drift is reduced from 96 MHz down to 6.6 MHz.