Grating enhanced external cavity diode laser

Abstract

We describe a concept for diode lasers with optical feedback. It is based on the combination of two different diode laser concepts: the diode laser with (i) feedback from a grating and (ii) resonant optical feedback from a separate cavity. The goal of our work is to unite the excellent tunability and well known reliability of grating diode lasers with the narrow emission linewidth of diode lasers with resonant optical feedback. Our theoretical description shows that a proper cavity design is essential for this concept. It also provides the means to optimize the cavity geometry. Our setup is based on an AR-coated laser diode emitting at 852 nm. It achieves an overall tuning range of 36.4 nm and a continuous tuning range of 45.1 GHz. A beat note measurement with a diode laser with resonant optical feedback demonstrates a short-term linewidth below 60 kHz. Continuous tuning ranges on the order of nanometers and linewidth on the order of kHz seem feasible.