Plasmonic Nanodisk Thin-Film Terahertz Photoconductive Antenna

Abstract

This paper presents the design, fabrication, and measurement of a plasmonic thin-film terahertz photoconductive antenna. Conventional terahertz photoconductive antennas suffer from poor optical-to-terahertz conversion efficiency, often on the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> . This is due to the low quantum efficiency of the device. The goal of this work is to demonstrate enhanced terahertz emission from a plasmonic thin-film device architecture. The combination of plasmonic nanodisks, a 120-nm low-temperature-grown gallium arsenide thin-film, and a bottom-located bowtie antenna has demonstrated the feasibility of producing such devices. Fabrication attempts and failure analysis is discussed in this work. Experimental characterization measuring the peak-to-peak electric field values of the terahertz pulses emitted from the device prototypes showed approximately five times improvement in plasmonic thin-film devices compared to conventional devices. The plasmonic thin-film devices had a measureable terahertz bandwidth of ~5 THz. This indicates that the plasmonic thin-film architecture has a potential for producing high optical-to-terahertz conversion efficiencies across a wide frequency range.