Diffraction limit investigation with sub-wavelength pixels

Current state-of-the-art pixel dimensions for both visible and long-wave infrared (LWIR) imagers are approaching the wavelength of measurement. It is expected that technological advances will continue and that sub-wavelength pixels for these wavebands will become a reality. In light of the diffraction limit, scientists and engineers in the visible and infrared domains have now begun pose the question as to whether it is worth having a focal plane array (FPA) with pixel dimensions smaller than the imaging wavelength. Meanwhile, in the terahertz domain, FPAs have already been fabricated and cameras designed around them with sub-wavelength pixels. INO has developed THz cameras with 160x120 pixels with pixel pitch of 52 μm and with 388 x 284 pixels with pixel pitch of 35 μm. The THz wavelength range is from 40 μm to 1000 μm and thus the focal plane array has pixel dimensions below that of the imaging wavelength. This paper discusses experimental results of diffraction limit investigation using sub-wavelength pixel THz cameras.