Imaging of broadband terahertz beams using an array of antenna-coupled microbolometers operating at room temperature
Spotlight summary: Microbolometric focal plane arrays (FPA) can be used to create video-rate terahertz (0.3-10 THz) imaging systems for security screening and medical diagnostics as well as for alignment and troubleshooting of terahertz equipment in a laboratory. The proof-of-principle demonstration of terahertz video-rate imaging has recently been performed using terahertz quantum cascade lasers and a commercially-available long-wavelength infrared microbolometric array (LWIR, λ=8-12μm) which have some residual absorption at terahertz frequencies.
Microbolometric FPAs optimized specifically for terahertz spectral range may offer significantly higher sensitivity for terahertz imaging; however, such FPAs were not available until very recently. The paper by Oden et al. reports one of the first uncooled microbolometric FPAs optimized for terahertz video-rate imaging. The unique feature of the reported FPA is the use of resonant THz antennas in each pixel, instead of broadband Salisbury screens employed in most microbolometric arrays. As a result, the sensitivity and time response of each pixel in the FPA can be optimized for a particular spectral range and multi-spectral terahertz imaging may be performed using broadband THz sources.
For the initial demonstration, a 320 x 240 array of antenna-coupled uncooled microbolometers was fabricated for operation at 2.2 THz. This FPA enabled, for the first time, video-rate imaging of broadband THz beams produced a photoconductive emitter in a THz time-domain spectroscopy setup using 40ms integration time per frame. Under these conditions, terahertz beams with detected power as low as 25 nW, corresponding to a power per pixel of 0.28 nW, were imaged with a signal-to-noise ratio better than 10, which corresponds to a noise level of approximately 27 pW. The latter is more than an order of magnitude lower than that of LWIR FPAs operated for terahertz video-rate imaging.
Technical Division: Optoelectronics
ToC Category: Detectors
|OCIS Codes:||(040.2235) Detectors : Far infrared or terahertz|
|(110.6795) Imaging systems : Terahertz imaging|
|(040.6808) Detectors : Thermal (uncooled) IR detectors, arrays and imaging|
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