Abstract-Efficient optical-to-terahertz conversion in large-area InGaAs photo-Dember emitters with increased indium content

 

I. E. Ilyakov, B. V. Shishkin, V. L. Malevich, D. S. Ponomarev, R. R. Galiev, A. Yu. Pavlov, A. E. Yachmenev, S. P. Kovalev, M. Chen, R. A. Akhmedzhanov,  R. A. Khabibullin, 

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-46-14-3360

In this Letter, optical-to-terahertz (THz) conversion of 800 nm femtosecond laser pulses in large-area bias-free InGaAs emitters based on photo-Dember (PD) and lateral photo-Dember (LPD) effects is experimentally investigated. We use metamorphic buffers to grow sub-micrometer thick In𝑥Ga1−𝑥As${\mathrm{I}\mathrm{n}}_x{\mathrm{G}\mathrm{a}}_{1-x}\mathrm{A}\mathrm{s}$ layers with indium mole fractions 𝑥=0.37$x=0.37$, 0.53, and 0.70 on a GaAs substrate. A strong enhancement of THz output energy with an increase of indium content is observed. On the surface of the sample providing the strongest emission (𝑥=0.7$x=0.7$), we have fabricated a 1.5cm2$1.5{\mathrm{c}\mathrm{m}}^2$ area of asymmetrically shaped metallic grating for LPD emission. This LPD emitter allows achieving high conversion efficiency of 0.24⋅10−3$0.24\cdot {10}^{-3}$ and a broad generation bandwidth of up to 6 THz. We also demonstrate that there is no significant difference in the conversion efficiency when operating at 1 and 200 kHz repetition rates. Our results show that large-area LPD emitters give a convenient, competitive way to generate intense high-repetition-rate THz pulses.

© 2021 Optical Society of America

Abstract-Plasmonic terahertz emitters with high-aspect ratio metal gratings

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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