Mid-Infrared Interband Cascade and Quantum Cascade Lasers for Chemcial Sensing

70109S02-II Monitoring the development and proliferation of nuclear materials and weapons is an important national objective. Several gases are emitted during the processing of nuclear materials, and their presence at trace levels essentially establishes that nuclear materials are being processed at a given location. However, presently available semiconductor lasers do not have the operating characteristics that would allow remote sensing units to covertly identify these gases. This project will insert a newly developed mid-infrared semiconductor laser into a transmitter system and demonstrate its functionality as a sensor unit that can covertly and remotely detect the presence of a nuclear-material-processing site. Phase I developed mid-infrared type-II interband cascade (IC) lasers, using intra-cavity-injection and improved optical cladding materials. In parallel, present generation, single-longitudinal mode, distributed-feedback (DFB) IC lasers were characterized and inserted into two different gas-detection systems, and the performance of these systems was evaluated. Specific strategies were developed for the effective detection, in the presence of typical atmospheric interference, of light and heavy compounds relevant to nuclear material processing. A design for a high sensitivity hydrocarbon sensor was completed. Phase II will demonstrate the use of high performance DFB IC lasers in a portable sensor for detecting gasoline vapors. A thermoelectrically-cooled IC Fabry-Perot (FP) laser, coupled to an external cavity that includes a grating element, will be demonstrated. The grating will allow for single-mode emission of the device in the 3-5 micron region with ~100nm of wavelength tunability. Finally, a cryogenically cooled FP quantum cascade laser will be demonstrated in an external cavity configuration showing similar tunability of a single mode emission in the 8-12 micron region. Commercial Applications and Other Benefits as described by awardee: The semiconductor diode lasers should enable not only a sensor system for detecting nuclear materials processing facilities but also a wide array of commercial products in several application areas. These areas include other chemical sensing applications (e.g., industrial process controls, medical diagnostics, explosives and bio-agent detection, etc.), free-space communications, and several military applications including infrared countermeasures.