CIPS/OSA Brown Bag Seminar Series

Thursday, November 13, 2008

12 noon , RLE Haus Conference Room 36-428

Lens-Coupled Terahertz Quantum Cascade Lasers and Real-Time Imaging

Alan Lee

Terahertz (THz) frequency range radiation, 0.3 THz to 10 THz (1 mm to 30 μm), has been used to demonstrate imaging of objects which are opaque at visible wavelengths: paints, packaging materials, tablet coatings in pharmaceuticals, and even illicit drugs in envelopes.  Terahertz quantum cascade lasers (QCLs) are good potential sources of illumination, because they are compact with multi-milliwatt power levels,  and have been engineered to operate at frequencies ranging from 1.2-5.0 THz (wavelengths of 60 - 250 um).  These long wavelengths require specialized waveguides for optical confinement– which leads to a tradeoff between output power, beam quality and operating temperature (178 K).  In this talk we demonstrate some of our work on minimizing this tradeoff, by butt-coupling QCL devices to index matched lenses.  This technique has also led to external-cavity, frequency-tunable QCLs.  These improvements are expected to impact our work on real-time terahertz imaging, which we demonstrate using a commercial microbolometer array detector.