Compact, robust, and spectrally pure diode-laser system with a filtered output and a tunable copy for absolute referencing

TL;DR

This paper presents a compact, stable diode-laser system with a filtered output and a tunable copy for absolute referencing, achieving high spectral purity and robustness suitable for atomic and molecular experiments.

Contribution

The design integrates a high-stability extended cavity diode laser with a pre-filter cavity and a tunable spectral copy, enabling simplified stabilization and high spectral purity.

Findings

PSD ≤ 100 Hz²/Hz in free-running mode

Sub-Hz PSD achieved with lock to ultra-stable reference

System is scalable and easy to operate

Abstract

We report on a design of a compact laser system composed of an extended cavity diode laser with high passive stability and a pre-filter Fabri-Perot cavity. The laser is frequency stabilized relative to the cavity using a serrodyne technique with a correction bandwidth of $\geq 6$ MHz and a dynamic range of $\geq 700$ MHz. The free running laser system has a power spectral density (PSD) $\leq 100$ Hz$^{2}$/Hz centered mainly in the acoustic frequency range. A highly tunable, $0.5-1.3$ GHz copy of the spectrally pure output beam is provided, which can be used for further stabilization of the laser system to an ultra-stable reference. We demonstrate a simple one-channel lock to such a reference that brings down the PSD to the sub-Hz level. The tuning, frequency stabilization and sideband imprinting is achieved by a minimum number of key elements comprising a fibered EOM (electro-optic modulator), AOM (acousto-optic modulator) and a NLTL (non-linear transmission line). The system is easy to operate, scalable, and highly applicable to atomic/molecular experiments demanding high spectral purity, long-term stability, and robustness.