A low-temperature external cavity diode laser for broad wavelength tuning

TL;DR

This paper presents a low-temperature external cavity diode laser system capable of broad wavelength tuning, enabling continuous coverage over tens of nanometers for various diode models, especially in the red spectrum below 633 nm.

Contribution

The work introduces a novel low-temperature ECDL design with combined thermoelectric and water cooling, expanding wavelength tuning capabilities for diode lasers in the red spectrum.

Findings

Achieved single-mode operation with 38 mW at 616.8 nm

Achieved 69 mW at 622.6 nm

Extended wavelength coverage over 15 nm below ambient

Abstract

We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64{\deg}C, more than 85{\deg}C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation was achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers and extending the wavelength coverage of commercial laser diodes.