Widely-tunable mid-infrared semiconductor lasers for spectroscopy applications and gas sensing

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This project aims to develop all-semiconductor tunable light sources with optical radiation in 3.05-3.45 µm (87-98 THz) and 4.25-4.65 µm (64-71 THz) spectral region for the detection and monitoring of gases including C2H2, CH4, C2H5, CH2O, CO, CO2 and N2O. The proposed technology is an electrically pumped difference-frequency generation device implemented in aluminum gallium arsenide. The structure of EP-DFG is an intra-cavity phase-matched Bragg reflection waveguide where the infrared light is generated by optically mixing the pump, which is an electrically injected multiple-quantum well diode laser embedded inside the waveguide core, and a signal which is delivered by an external source. EP-DFGs are potential sources for applications in infrared absorption spectroscopy where a continuously tunable source is desired. Available IR sources such as quantum-cascade lasers generally inherit wavelength tunability in range of few nanometers. EP-DFGs enable wavelength tunability in range of hundreds of nanometers offered by detuning the pump wavelength, the signal wavelength or detuning simultaneously both pump and signal wavelengths. An example of commercial potential of EP-DFG devices is continuous sensing and monitoring of gases where wavelength tunablity enables precise scanning of the absorption lines of the molecules and their isotopes. Another application is multi-component gas analysis which requires tunable lasers since they can access a wide spectral range that usually contains several absorption lines of the molecules. The availability of single tunable lasing devices such as EP-DFGs can replace several conventional lasers, resulting in reduced cost and compact assembly component.