1PhD student, Department of Electrical and Computer Engineering, Tarbiat Modarres
2Professor of Electrical and Computer Engineering, Tarbiat Modarres
3School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran.
We propose a new generation of unbiased (bias-free) antenna-less CW THz photomixer emitters array made of asymmetric MSM gratings with subwavelength pitch, operating in optical near-field regime. We take advantage of the size effects in near-field optics and electrostatics to demonstrate the possibility of enhancing the THz power by four orders of magnitude, as compared with a similar array of the same size that operates in the far-field regime. We show that with an appropriate choice of grating parameters in such THz sources the first plasmonic resonant cavity mode in nano-slit between two adjacent MSM can enhance the optical near-field absorption and hence the photo carriers’ generation under the slit in the active medium. These photo carriers, on the other hand, are accelerated by the large built-in electric field sustained under the nano-slits by two dissimilar Schottky barriers to create the desired large THz power that is mainly radiated downward. A hybrid numerical simulation method is used to model and analyze these phenomena.