A simple system of thermal control and frequency stabilization of solitary diode lasers

A temperature controller using the photodiode of a free-running laser as a heater element is described. Its use can improve substantially the stabilization on a spectroscopic line and avoids the need of sink temperature controller at the millidegrees kelvin level. The long term stability of the system has been tested in performing a detailed study of the splitting of the dark lines in rubidium vapors.