This Small Business Innovation Research (SBIR) Phase I project will develop mid-infrared (IR) quantum cascade lasers based on type-II indium arsenide/gallium anitmonide/aluminum antimonide (InAs/GaSb/AlSb) quantum well structures. These lasers emit radiation in the mid-IR region, enabling commercial products in fields including chemical sensing, medical diagnostics, and industrial process controls. The wavelength of Sb-based quantum cascade lasers can be tailored over a wide spectral range due to the large conduction band-offset between InAs and AlSb. In addition, because of the band-gap blocking in type-II quantum well structures, electron injection efficiencies near 100% can be achieved without requiring Bragg reflector layers. Another advantage of this material system is the small electron effective mass in InAs, contributing to reduced phonon scattering rates. Hence, the inter-sub-band quantum cascade lasers based on type-II InAs/GaSb/AlSb quantum well structures are excellent candidates for compact, reliable, efficient mid-infrared light sources operating at room temperature. Phase I will involve the design, molecular beam epitaxy (MBE) growth, characterization, and optimization of InAs/GaInSb/AlSb quantum cascade lasers to demonstrate their feasibility of operation at low threshold current and at ambient temperatures (or at temperatures accessible with a thermoelectric cooler). High performance mid-IR quantum cascade lasers would be developed in Phase II.
The first mid-IR semiconductor lasers are expected to operate under continuous wave (cw) conditions at ambient temperatures. This would enable commercial products in several fields including chemical sensing. One example is detection, at the parts per billion (ppb) level, of formaldehyde and related compounds for medical diagnosis purposes. These laser sources will potentially find other commercial and defense applications.
