Plasmonic photoconductive antennas for terahertz pulsed spectroscopy and imaging systems

We propose a terahertz (THz) plasmonic photoconductive antenna (PCA) with a record height of its metal electrodes of $h$ = 100 nm and a high aspect ratio of $h/p$ = 0.5 ($p$ is the period of the plasmonic grating) that can be used as a source is THz pulsed spectroscopic and imaging systems. We experimentally demonstrate that the power of the THz radiation generated by the proposed plasmonic PCA is two orders of magnitude higher than that of an equivalent ordinary PCA without a plasmonic grating. Current–voltage measurements of the thus developed plasmonic PCA under femtosecond laser excitation show that the photocurrent of the PCA increases 15-fold, up to $i _p\approx$ 1.2 mA. To reduce the leakage currents of the PCA, we propose a fabrication technology that is based on the etching of windows in a thin Si$_{3}$N$_{4}$ passivation dielectric layer deposited on the photoconductor surface, which makes it possible to reduce the dark current to $i_d\approx$ 5 $\mu$A.