Antenna coupled GaN-based pulsed THz emitter array, enhanced with nano-slit plasmonic waveguide modes

Abstract

An array of unbiased pulsed GaN-based terahertz emitters based on excitation of different waveguide modes in the metallic contact grating is proposed and simulated for the first time. The proposed emitter consists asymmetric metal semiconductor-metal, so dissimilar Schottky contacts induce internal electric field that accelerates the photogenerated carriers. Furthermore, by taking advantage of plasmonic cavity modes for specific dimensions of the emitter array, it is shown that THz photocurrent can be enhanced about 5 times in comparison with the unbiased emitter array of the same area. We demonstrate that, for appropriate dimensions of the top metal contact in such a THz emitter array, the first order guided modes of the sub-wavelength nano-slit waveguides will be formed between two adjusted metal contacts, which leading to an enhanced optical absorption and the consequent THz photocurrent in the active region. Finally, we have designed a THz antenna with maximum gain of 6.5, and bandwidth of 400 GHz, which is coupled to the proposed THz emitter array to improve the output radiation power.