Design of a Littrow-type diode laser with independent control of cavity length and grating rotation

TL;DR

This paper introduces a novel Littrow-type extended-cavity diode laser design that allows independent control of cavity length and grating rotation, enhancing stability and tunability for atomic and molecular applications.

Contribution

The design decouples coarse wavelength adjustment from fine cavity tuning, improving robustness against misalignment and hysteresis in extended-cavity diode lasers.

Findings

Mode-hop-free frequency tunability exceeds external cavity free spectral range.

Two prototypes demonstrated stable locking to atomic references.

Design is suitable for high-stability atomic and molecular experiments.

Abstract

We present a novel extended-cavity diode laser (ECDL) based on a modified Littrow configuration. The coarse wavelength adjustment via the rotation of a diffraction grating is decoupled from the fine tuning of the external cavity modes by positioning a piezo transducer behind the diode laser, making the laser robust against misalignment and hysteresis even with long external cavities. Two laser prototypes with external cavities of different lengths were tested with a 780 nm laser diode, and locked to an atomic reference. We observe a mode-hop-free frequency tunability broader than the free spectral range of the external cavity upon changes of its length. The design is well suited to atomic and molecular experiments demanding a high level of stability over time.