Collaborative research: Compact room temperature operated THz emitters with scalable architecture and low electric power consumption

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Abstract Title: Compact and efficient room temperature operated terahertz emitters for industrial, medical and home security applications. Nontechnical: Terahertz sensing is an enabling technology for noninvasive detection of biological and chemical hazardous agents, cancer detection, detection of mines and explosives, security screening in buildings, airports, and other public space, as well as short-range covert communications in terahertz transmission windows of the atmosphere. Currently available terahertz sources are either bulky or require cryogenic cooling leading to high costs, high complexity, and often low reliability. The proposed novel design concept aims to address most of the deficiencies of the current state-of-the-art terahertz emitter technology. The target device implementation will be similar in terms of the complexity, reliability and size to widely used standard inexpensive near infrared diode lasers. The success of the proposed effort will enable wide deployment of terahertz imaging and spectroscopic sensors for the security screening, medical diagnostics, and industrial monitoring applications. The project requires strongly correlated effort between theory and experiment including extensive modeling, optimization of the device fabrication methodologies as well as detailed characterization and field testing of the novel laser emitters. The research effort is integrated with educational and outreach plans aimed at enhancing education opportunities at the New York and Texas public universities and local communities. Technical: The main goal of the project is the development of high-power diode lasers with built-in resonant nonlinearity for efficient intra-cavity difference frequency generation in the terahertz spectral range. The gain sections based on asymmetric coupled quantum wells utilize the unique band alignment that can be realized in an antimonide material system. Laser modes generated at two closely spaced wavelengths near 2 microns will serve as an intracavity pump field for difference frequency generation. The antimonide-based diode lasers emitting in that spectral region demonstrate some of the lowest threshold current densities ever achieved for semiconductor lasers, excellent temperature stability, and watt level output power, all at room temperature. The expected electrical power input necessary for the proposed device operation with micro to milliwatt terahertz output level will be two to three orders of magnitude lower than those of existing technologies. The proposed research offers experimental and theoretical studies of the fundamental problem of resonant optical nonlinearities in antimonide-based quantum-well systems in a wide range of carrier populations from nondegenerate to highly degenerate. The future development of the proposed devices will include fabrication of widely tunable terahertz emitters as well as integration with silicon photonics. Transfer of the technology to the arsenide or silicon platform will enable epi-side down mounting of large area arrays of the terahertz emitters to scale up the output terahertz power to tens of milliwatt level and perform terahertz beam shaping.