A Reflection Based, Pulsed THz Imaging System with 1 mm Spatial Resolution

Operating in reflection and using single pixel, whiskbroom scanning to generate images, we report on a THz imaging system with a spatial resolution of 1 mm and a post detection SNR of 67 dB. The source in the system is an ErAs:GaAs photoconductive switch, , and the detector is a waveguide mounted, zero-bias Schottky diode operating at a center frequency of 600 GHz and a 3 dB bandwidth of 200 GHz. The high output power of the photoconductive switch and large instantaneous bandwidth of both switch and detector allow the system to achieve this high post detection SNR in a 60 Hz bandwidth when reflecting off a specular metal target at a standoff of 4 cm. The spatial resolution is superior to that predicted by the standard Rayleigh criterion as expected from the systems' Gaussian (non uniform) illumination, but is inferior to the Sparrow Criterion due to the presence of system noise, and discrete rounding of sample amplitudes.