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18 February 2010 Coherent imaging at 2.4 THz with a CW quantum cascade laser transmitter
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A coherent transceiver using a THz quantum cascade laser as the transmitter and an optically pumped molecular laser as the local oscillator has been used, with a pair of Schottky diode mixers in the receiver and reference channels, to acquire high-resolution images of fully illuminated targets, including scale models. Phase stability of the received signal, sufficient to allow coherent image processing of the rotating target (in azimuth and elevation), was obtained by frequency-locking the TQCL to the free-running, highly stable optically pumped molecular laser. While the range to the target was limited by the available TQCL power (several hundred microwatts) and reasonably strong indoor atmospheric attenuation at 2.408 THz (2.0 dB/m at 40% RH), the coherence length of the QCL transmitter will allow coherent imaging over distances up to several hundred meters. In contrast to non-coherent heterodyne detection, coherent imaging allows signal integration over time intervals considerably longer than the reciprocal of the source, or signal bandwidth, with consequent improvement in the signal-to-noise ratio. Image data obtained with the system will be presented.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andriy A. Danylov, Thomas M. Goyette, Jerry Waldman, Michael J. Coulombe, Andrew J. Gatesman, Robert H. Giles, Xifeng Qian, Neelima Chandrayan, Shivashankar Vangala, Krongtip Termkoa, William D. Goodhue, and William E. Nixon "Coherent imaging at 2.4 THz with a CW quantum cascade laser transmitter", Proc. SPIE 7601, Terahertz Technology and Applications III, 760105 (18 February 2010);

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