Bias-free Terahertz Generation through Graded-composition InGaAs Photoconductive Structures

We present a bias-free photoconductive terahertz emitter that utilizes the deep built-in electric field in a graded-composition InGaAs structure to generate terahertz radiation at $\sim 1550$ nm optical pump wavelength. A plasmonic nanoantenna array is employed to confine photo-generated carriers in regions with the highest built-in electric field. We demonstrate record-high-power pulsed terahertz generation compared to other photoconductive emitters operating in the 1550 nm optical wavelength range, with power levels exceeding 860μW.