A customized terahertz time-domain spectroscopy system for phase-resolved measurements of active semiconductor quantum devices

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The external performance of nanoelectronic and quantum optoelectronic devices such as quantum cascade lasers, semiconductor quantum well photodetectors, semiconductor optical amplifier, etc, is governed by their inner workings as described by modal gain, optical loss, free carrier absorption, carrier transport. Without an experimental means of probing these crucial parameters, the chief mechanisms responsible for sub par device performance remain speculative at best. This award provides essential support for the acquisition of needed components and instruments, in combination with an existing mode-lock Ti:Sapphire laser, to complete a terahertz time-domain spectroscopy (THz-TDS) system. The THz-TDS system will be used to carry out temperature-dependent, phase-resolved, time-resolved measurements of lasing emission from a terahertz quantum cascade laser with a metal-metal waveguide. This home-integrated system will be a very versatile and enabling tool for different research purposes. The proposed system is particularly an indispensible tool for the applicant's ongoing research projects on semiconductor quantum optoelectronic devices. It will provide vital capabilities to our research on: 1) development and characterization of THz quantum cascade lasers; 2) investigation of internal dynamic processes of quantum semiconductor heterostructures; 3) optimization of terahertz quantum cascade lasers for high-temperature and high power operation; 4) exploration of terahertz amplifiers and terahertz detectors based on semiconductor quantum structures. It will significantly leverage our research efforts in developing high-performance semiconductor components for THz imaging, bio- and environmental sensing application. In addition, it will help extend our research into new areas such as nanotechnology and nanoelectronic devices. Not only does the proposed system fit the most demanding research application, it is a great teaching tool for our graduate students and other HQP. The availability of this THz-time-domain spectroscopy system will enrich the research and education opportunities to our undergraduate and graduate students from the engineering programs.