Browsing by Author "Belyanin, Alexey"

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Collaborative Research: Quantum Cascade Laser Transceivers for Terahertz Wireless Communication
Physics And Astronomy; TAMU; https://hdl.handle.net/20.500.14641/626; National Science Foundation
The terahertz is a region of the electromagnetic spectrum lying between microwaves and the infrared range, also known as the "terahertz gap" due to the lack of suitable technologies for its generation and manipulation. On the one hand, conventional electronic devices used to produce microwaves cannot operate at higher frequencies, while on the other hand optical sources such as terahertz lasers typically require cryogenic operation, which is impractical. Thus, novel approaches are needed to develop convenient terahertz sources. The goal of this project is to demonstrate a new class of terahertz sources based on a high-power mid-infrared semiconductor laser (so-called quantum cascade laser) designed to generate a comb of frequencies separated by precisely equidistant terahertz frequency intervals. The resulting terahertz radiation sources will show room temperature operation, narrow linewidth, and wide tunability. These would be attractive for many applications, especially remote sensing. Indeed, hundreds of chemicals from gases to drugs, explosives, and biomolecules have telltale absorption and emission features in the terahertz range. Terahertz sensing would allow one to monitor the ozone depletion, climate change, and environmental pollution. It would give insights into the formation and decay of stars in our galaxy and beyond. Such terahertz sources would also be very valuable in the studies of materials, since many fundamental excitations in matter such as plasma oscillations and sound waves exhibit resonances in the terahertz. The core of the proposed new device architecture consists of a mid-infrared quantum cascade laser generating an optical frequency comb with a terahertz spacing between longitudinal modes, named a harmonic frequency comb. However, instead of using infrared light emitted from the laser as in typical frequency combs, here the intracavity beating of the optical modes constituting the comb is exploited to generate a coherent terahertz signal at room temperature. The focus of this project is to demonstrate such new terahertz sources for sensing applications. These devices will benefit from unprecedented compactness, having a footprint smaller than 1 square centimeter. Thanks to the nature of a frequency comb, they will generate terahertz tones with narrow linewidth (in the Hz range) and high stability. Moreover, they will be able to operate at room temperature with a broad tuning range, from microwaves to the terahertz region, as a result of the fast electron dynamics of the laser. By connecting and synchronizing an array of such devices, it will be possible to coherently scale up the emitted power and enable terahertz beam control, such as beam steering and shaping. Because of these unique features, the proposed sources will rival and potentially outperform other existing systems for terahertz sensing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
Collaborative Research: Compact Room Temperature Operated THz Emitters-With Scalable Architecture and Low Electric Power Consumption
Physics And Astronomy; TAMU; https://hdl.handle.net/20.500.14641/626; National Science Foundation
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.