Efficient THz emission by a photoconductive emitter with tight photocarrier confinement within high-aspect ratio plasmonic electrodes

We propose, simulate and investigate how the thickness of plasmonic electrode h and the ratio between h and the period of subwavelength periodical metallic (plasmonic) grating $h/p$ on the THz emission efficiency in a photoconductive emitter. By numerical optimization we determine the grating geometry with respect to maximal optical transmission. We showcase that simultaneous increase in $h$ and $h/p$ allows efficient excitation of plasmon modes in the grating, that follows with an THz power enhancement up to 10000 compared to conventional emitter without grating. The overall THz power exceeds 5 $\mu$W in the 0.1–4 THz bandwidth, with the conversion efficiency of $\sim$0.2%. The developed grating design can be also used for photoconductive THz detectors in modern THz spectroscopic and imaging setups.