SBIR Phase I: Tunable Terahertz Quantum Cascade Lasers for Spectroscopy

This Small Business Innovation Research (SBIR) Phase I project will focus on the demonstration of a frequency tunable quantum cascade laser (QCL) operating at terahertz frequencies (1-10 THz) for applications including spectroscopy and non-destructive imaging. This novel source is based on external micropositioning driver for actuated the tuning mechanism that manipulates the QCL's optical waveguide dimensions. This manipulation effectively changes the optical index of the waveguide and the emission frequency of the QCL. The frequency tuning will be actuated electronically, resulting in fast sweeps (>100 Hz) over frequency ranges of>300 GHz. The tunable QCL will be housed in a small footprint cry cooler, and will have output powers greater than 100µW - an improvement of 3 orders of magnitude over current commercial systems. Phase II improvements will result in larger tunable ranges at center frequencies ranging from 1.5 to 5 THz. The broader impact/commercial potential of this project will be in detection and characterization of narrow gas lines (MHz) or solid absorption features (GHz) in spectroscopy or spectroscopic imaging, useable for academic, industrial and governmental research. The electrical operation of the MEMS tunable source and the turnkey nature of the cryogenic system will allow non-expert researcher access to the terahertz spectral region. Future uses include incorporation into a swept-source optical coherence tomography system for non-destructive evaluation (NDE). Terahertz frequency radiation is of particular interest for use in NDE because they are able to penetrate materials that are opaque at infrared and visible wavelengths such as structural foams, polymers and paints. Potential applications include the validation of the structural integrity of foams used in the aerospace industry; continuous monitoring of paint processes in the automotive industry; and the validation of pharmaceuticals tablet coatings used in controlled release formulations.