Radiation Enhancement in Plasmonic Bias-free and Antenna-less CW Terahertz Photomixer Emitters Array

Mohammad Zamani, Mohammad Javad; Moravvekj Farshi, Mohammad Kazem; Neshat, Mohammad

Radiation Enhancement in Plasmonic Bias-free and Antenna-less CW Terahertz Photomixer Emitters Array

Authors

M. J. Mohammad zamani ¹

M. K. Moravvekj farshi ²

M. Neshat ³

¹ PhD student, Department of Electrical and Computer Engineering, Tarbiat Modarres

² Professor of Electrical and Computer Engineering, Tarbiat Modarres

³ School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran.

Abstract

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.

Keywords

Photomixer

Terahertz Emitters

Metal-Semiconductor-Metal

Plasmonics

Subwave-length structures