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-Terahertz radiation from an InAs surface due to lateral photocurrent transients

P. Cicėnas, A. Geižutis, V. L. Malevich, and A. Krotkus
https://www.osapublishing.org/ol/abstract.cfm?URI=ol-40-22-5164

We report on terahertz (THz) emission from a (111)-cut InAs crystal in the reflection and transmission directions, excited by femtosecond optical pulses in the direction of its surface normal. THz pulse amplitudes emitted from the crystal surface in this case were only ∼20% smaller than for optimal photoexcitation at a 45° angle. This observation evidences that THz emission from InAs is caused by lateral photocurrent transients appearing due to a crystal anisotropy rather than directly by the photo-Dember effect, which creates fast changing electric polarization perpendicular to the surface. Such a simple geometry of the photoexcitation could greatly enhance the fields of surface THz emitter applications.

© 2015 Optical Society of America

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