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 the 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 °C, more than 85 °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 is 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.
Highlights
Diode lasers are compact, robust optical sources with a broad range of applications in physics research
We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning
For two different diode models, single-mode operation is 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
Summary
Robust optical sources with a broad range of applications in physics research. While many commercial diode products based on AlGaInP semiconductors exist for red wavelengths above 630 nm, few exist for the wavelengths below. Laser diode wavelengths typically tune between 0.15 and 0.25 nm/◦C due to temperature-dependent changes in the gain profile of the semiconductor diode materials and the length of the laser cavity.. We present a temperature-tunable ECDL that achieves an operating temperature of −64 ◦C, which extends the tuning range of a red laser diode by more than 15 nm from its nominal operating wavelength. We present measurements and calculations of thermal load for this design and characterize the performance of 633 nm and 638 nm laser diodes in the low temperature regime. The laser system could be used for the broad tuning of different laser diode models at a variety of wavelengths with minor modifications
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