Narrow frequency-band laser with optical feedback

Abstract

In this paper we discuss the construction of a narrow frequency-band laser with optical feedback. We use a distributed Bragg reflector (DBR) laser diode centered at the cesium D₂ transition wavelength, [gamma] = 852 nm. The linewidth of this diode is reduced by several orders of magnitude by means of optical feedback from an external cavity. The system is further stabilized by locking the path length between diode and cavity to optimize coupling between them. The absolute frequency of our laser is fixed by means of a delay line lock system that uses the beat note between our laser and a fixed reference laser to set our laser's frequency. We present both the theory behind these systems and data from our own setup. We then finally discuss potential uses of the narrow laser in atomic physics experiments, including detection of a single atom in an optical cavity.