D. V. Lavrukhin, A. E. Yachmenev, I. A. Glinskiy, R. A. Khabibullin, M. Ryzhii, T. Otsuji, M. Shur, K. I. Zaytsev, D. S. Ponomarev
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11022/1102203/Plasmonic-terahertz-emitters-with-high-aspect-ratio-metal-gratings/10.1117/12.2521290.short
We propose a novel technology for fabricating
plasmonic photoconductive antennas (PCAs) based on superlattice (SL) with
increased height of the plasmonic gratings up to 100 nm. We passivate the surface
of the SL by Si3N4, etch there windows and deposit Ti/Au antenna
metallization. The plasmonic gratings are formed by electron-beam lithography
with Ti/Au metallization followed by lift-off. Then an Al2O3 anti-reflection
coating layer for reduction of the Fresnel reflection losses is used on the top
of the plasmonic gratings, which also serves for maintaining its mechanical
stability and providing the excitation of guided modes at the resonant
wavelengths of the subwavelength slab waveguide formed by the metal gratings.
Current-voltage measurements under femtosecond laser illumination reveal strong
increase of the transient photocurrent generated by the fabricated plasmonic
PCA which is 15 times higher than for conventional one (i.e. without the
plasmonic gratings). The obtained terahertz (THz) power spectra demonstrate
100-times increase of the THz power in the plasmonic PCA. The results might be
of interest to the needs of THz spectroscopy and imaging systems, in
particular, operating with low-power lasers.
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