GaSb-Based Diode Lasers for Remote Detection of Carbon Dioxide
- Wednesday, 01 January 2014
- NASA’s Jet Propulsion Laboratory, Pasadena, California
Lidar systems measure carbon dioxide to understand better the impact of the carbon cycle on global warming and climate change.
Monolithic ridge-waveguide GaSbbased diode lasers were fabricated with a second-order, laterally etched Bragg grating to generate single-mode emission from InGaAsSb/AlGaAsSb multiquantum- well structures. In this design, the monolithic Type-I GaSb-based diode lasers use grating structures that exhibit low internal loss. The frequency-stable diode lasers meet the needs of high power (>50 mW) and narrow linewidth (≈100 kHz). These devices are strong candidates for replacement of the solidstate light sources. Furthermore, this design is not limited to this wavelength. By optimizing the quantum well, and the optical design, this innovation can adapt to any wavelength within the 2-to-3-μm spectral window with similar performance.
Commercial semiconductor distributed- feedback (DFB) lasers emitting at 2 μm are limited in power because of Auger recombination and other loss mechanisms at longer wavelengths on InP-based diode lasers. Additionally, GaSb-based LC-DFB (laterally-coupled distributed feedback) laser designs that incorporate metal gratings generate additional absorption loss in the laser cavity, limiting output power to approximately 10 mW. The lasers reported here exhibit low internal loss, making them suitable for high-power applications.