Continuous Wave Terahertz Source Photonic Band Engineering

The terahertz wave region of the electromagnetic spectrum offers exciting and unique attributes for security imaging and secure broadband communications. However, THz signal generation is difficult and current applications are rare. Existing THz sources utilize large and expensive lasers operating in pulsed mode. Practical application of THz radiation requires the development of THz source technology that is energy efficient, cost effective and provides continuous emission with high temporal and spatial coherence. Recent progress in photonic band gap engineering holds the promise of realizing a highly efficient coherent THz laser in a truly cost effective manner. In the Phase I program, a PBG THz generator consisting of a periodic structure of ZnTe and fused quartz was fabricated by an optical bonding technique. Terahertz generation was successfully demonstrated with this device and the enhancement of THz generation arising from PBG structure was observed. In the proposed Phase II program, further improvements in material selection, PBG structure design, fabrication technique, and signal enhancement are expected to produce highly coherent and directional CW THz radiation with high power level, narrow linewidth and frequency tunability. A prototype system for security imaging through fabric and paper will be built and tested using this source.