Terahertz Inverse Synthetic Aperture Radar (ISAR) Imaging With a Quantum Cascade Laser Transmitter
NATIONAL GROUND INTELLIGENCE CENTER CHARLOTTESVILLE VA
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A coherent transceiver using a THz quantum cascade TQCL 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 and concealed objects. 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, the coherence length of the TQCL transmitter will allow coherent imaging over distances up to several hundred meters. Image data obtained with the system is presented.
- Lasers and Masers
- Miscellaneous Detection and Detectors
- Active and Passive Radar Detection and Equipment
- Quantum Theory and Relativity