Anisotropic Semiconductor Crystals for Terahertz Frequencies

Terahertz (THz) technology shows great promise for threat detection and imaging of concealed weapons, explosives, chemical and biological agents, luggage at airport security checkpoints, and medical diagnostics. THz frequencies however have not been fully and successfully utilized because of a lack of compact high power sources and high efficiency detectors. To address these needs, EIC Laboratories proposes to grow large-area, defect free ultrapure nonlinear optical crystals for generating and detecting THz radiation in the 0.3 – 20 THz range (10-600 cm-1). In Phase I, we have investigated various high and narrow bandgap semiconductor crystals for their THz performance as emitters and/or detectors. Among these semiconductors, covering a wide THz spectrum from 100 GHz to 40 THz, we have identified a few for in-detail investigation in the Phase II effort. The Phase II research will concentrate on producing defect-free, high optical quality, large crystals from zone-refined precursor materials using vertical modified Bridgman technique. Extensive growth modeling/simulation and crystal characterization will be used to optimize crystal growth conditions. The performance of these materials as THz sources and sensors will be evaluated. Practical applications of the THz crystals in explosives and non-explosives detection, bio molecules, various amino acids forming proteins and personnel identification by hair and skin analysis will be demonstrated.