Optimization of a 3.6-THz quantum cascade laser for real-time imaging with a microbolometer focal plane array

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Author
Behnken, Barry
Karunasiri, Gamani
Chamberlin, Danielle
Robrish, Peter
Faist, Jérôme
Date
2008Metadata
Show full item recordAbstract
Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum cascade laser (QCL) and
an uncooled, 160x120 pixel microbolometer camera fitted with a picarin lens. Noise equivalent temperature difference
of the camera in the 1-5 THz frequency range was calculated to be at least 3 K, confirming the need for external THz
illumination when imaging in this frequency regime. After evaluating the effects of various operating parameters on
laser performance, the QCL found to perform optimally at 1.9 A in pulsed mode with a 300 kHz repetition rate and
10-20% duty cycle; average output power was approximately 1 mW. Under this scheme, a series of metallic objects
were imaged while wrapped in various obscurants. Single-frame and extended video recordings demonstrate strong
contrast between metallic materials and those of plastic, cloth, and paper—supporting the viability of this imaging
technology in security screening applications. Thermal effects arising from Joule heating of the laser were found to be
the dominant issue affecting output power and image quality; these effects were mitigated by limiting laser pulse widths
to 670 ns and operating the system under closed-cycle refrigeration at a temperature of 10 K.
Description
The article of record as published may be found at http://dx.doi.org/10.1117/12.767671
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
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