High-Power, Narrow Linewidth Laser Diodes for Alkali Atoms

Semiconductor lasers are fabricated in large volumes and are available at low prices at a wide variety of wavelengths for many commercial applications. These applications have modest requirements for power, beam quality, and reliability. The recent growth in metrology applications has necessitated class of lasers that operate stably within a single spatial and longitudinal mode, with wavelength that corresponds to a specific atomic transition. Photodigm produces high power distributed Bragg reflector (DBR) lasers based on its proprietary single epi growth, ridge waveguide architecture. The company is currently shipping single frequency lasers to several DoD programs for precision metrology at wavelengths of 1083 and 780 nm. In this proposed Phase I effort, Photodigm will design an epitaxial structure targeting the cesium transition at 852 nm. To minimize execution risk, this structure will be based on our proven 780 nm design. Two fabrication cycles will be needed to calibrate the grating period to meet the tight wavelength specification for atomic spectroscopy. The performance and the lifetime of these laser diodes will be directly compared to existing DBR laser diodes emitting at 780 nm. First articles will be delivered to DARPA. The Phase II effort will focus on higher powers and additional wavelengths.