An Optically Narrowed Diode Laser for Rb Saturation Spectroscopy

Abstract
Diode laser linewidths have been reduced by a factor of up to 20 000 using the technique of resonant optical feedback. In this method, the laser frequency also locks optically to a confocal cavity, greatly improving the passive frequency stability. For the first time, such an optically narrowed diode laser has been used to obtain high-resolution Doppler-free spectra of the D2 line of 85Rb and 87Rb at 780 nm.