SBIR Phase I: A diode laser system for high-resolution terahertz spectroscopy

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This Small Business Innovation Research Phase I project will develop a turnkey laser system for creating terahertz radiation by optical heterodyne mixing of two laser frequencies on a solid-state photomixer. In Phase I the lasers will tune relative to each other over a range of 0 to 1 THz with 2 MHz absolute accuracy and 2 MHz relative linewidth. To achieve this performance, novel frequency-offset locking techniques will be used to maintain laser locking with 100% duty cycle to absolute frequency references during the entire tuning range. The laser system will be all solid state, robust, and easy to use, making it a key enabling technology, along with commercially available photomixers, for the commercialization of high-resolution cw terahertz spectrometers. High-resolution terahertz spectrometers will provide a new window into low-energy light/matter interactions and can directly probe large amplitude vibration motions of molecules, DNA, biomolecules, and proteins. A high-resolution terahertz spectrometer will have important applications to biomolecular research, pharmaceutical development, and homeland security. Large molecules such as proteins, DNA, and even bacteria and viruses can have spectroscopic signatures in the terahertz regime with clear applications to bio-threat detection and research and development. Research is showing that different crystalline forms of large molecules have signatures in terahertz regime with important consequences for drug uptake and process control of pharmaceuticals. Terahertz spectrometers could also aid in the R&D of antibody/antigen receptors important to drug research and biomolecular research. Finally, spectroscopic signatures of large molecules could have a large impact on explosives detection for landmine remediation efforts and transportation and building security.