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

该项目旨在开发3.05-3.45微米(87-98太赫兹)和4.25-4.65微米(-71太赫兹)光谱范围的光辐射全半导体可调光源，用于检测和监测包括C2H2、CH4、C2H5、CH2O、CO、CO2和N2O在内的气体。所提出的技术是一种在铝化镓中实现的电泵浦差频产生装置。EP-DFG的结构是腔内相位匹配的布拉格反射光波导，红外光是通过光学混合泵浦产生的，泵浦是嵌入在波导芯中的电注入多量子阱半导体激光器，信号由外部源传输。EP-DFGs是红外吸收光谱中需要连续可调谐光源的潜在光源。现有的红外光源，如量子级联激光器，通常在几个纳米的范围内继承了波长的可调性。EP-DFG通过对泵浦波长、信号波长或同时对泵浦波长和信号波长进行失谐来实现数百纳米范围内的波长可调谐。EP-DFG设备的商业潜力的一个例子是对气体的连续传感和监测，其中波长可调使分子及其同位素的吸收线能够精确扫描。另一种应用是多组分气体分析，这需要可调谐激光，因为它们可以访问通常包含分子的几条吸收线的宽光谱范围。单个可调谐激光器件的出现，如EP-DFG，可以取代几个传统的激光器，从而降低了成本和紧凑的组装组件。

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.