Strain-induced photoconductive THz detectors for high-speed spectroscopy and imaging

Abstract

Photoconductive THz antennas (PCAs) are intensively used in modern time-domain spectroscopic and imaging setups thanks to their reliability, cost-effectiveness, simplicity of fabrication, and their flexibility in
the designing of antenna electrodes and topology, as well as the choice of photoconductive substrate. Compared with the existing THz devices [1,2], PCAs can efficiently work at room temperature demonstrating a broadband spectrum of 0.1-5.0 THz with a perfect dynamic range, i.e. signal-to-noise ratio exceeding even 100 dB [3]. Recently, the Ge-based PCAs have demonstrated an unprecedented bandwidth reaching 70 THz thanks to an absence of polar phonons in Ge [4]. Moreover, an optical-to-THz conversion efficiency of the PCA is not limited by the Manley-Rowe relation [5], as the photoconductivity theoretically allows converting every single optical photon into one electron-hole pair. Nevertheless, an increase of the spectrometer sensitivity, that is determined by the signal-to-noise ratio of a PCA-detector, is still in progress and requires additional solutions.

We report our recent approach on the new designed PCA-detector, that relies on the strain-induced InGaAs/InAlAs superlattice, providing an efficient operation at both 780 nm and 1550 nm laser excitation. In 2019 we proposed [6] that artificially strained SLs might be efficiently used for the PCA-detectors since they allow sub-picosecond photocarrier lifetimes with moderate mobility without using any compensating p-type dopants during fabrication. Then, we fabricated the PCA-detector and showed its advances over conventional (and commercial) detector that utilizes lattice-matched (LM) InGaAs/InAlAs SL [7]. The 3.5 THz detection bandwidth and signal-to-noise (S/N) ratio above 70 dB are reached. The strain-induced detector shows
quadratic dependence of its S/N ratio on probe beam power, while the S/N ratio for LM PCA-detector saturates at 5 mW. The first also demonstrates almost independent noise level of probe beam power, which is a crucial feature of the detector. We thus believe that strain-induced PCA-detector coupled to a fiber telecom wavelength laser, could open a pathway toward the development of portable and cost-effective THz photoconductive devices.

1. P.U. Jepsen, D.G. Cooke, and M. Koch. "Terahertz spectroscopy and imaging – Modern techniques and applications". Las. Photon. Rev. 5, 124, 2011.
2. A.E. Yachmenev, R.A. Khabibullin and D.S. Ponomarev. "Recent advances in THz detectors based on semiconductor structures with quantum confinement: a review". J. Phys. D: Appl. Phys., 55(19), 193001, 2022.
3. R.B. Kohlhaas, S. Breuer, L. Liebermeister et al. "637 μW emitted terahertz power from photoconductive antennas based on rhodium doped InGaAs". Appl. Phys. Lett., 117, 131105, 2020.
4. A. Singh, A. Pashkin, S. Winnerl et al. "Up to 70 THz bandwidth from an implanted Ge photoconductive antenna excited by a femtosecond Er:fibre laser". Light: Sci. Appl., 9, 30, 2020.
5. A. Petukhov, V. Brudny, W. Mochàn et al. "Energy conservation and the Manley-Rowe relations in surface nonlinear-optical spectroscopy". Phys. Rev. Lett., 81, 566, 1998.
6. D.S. Ponomarev, A. Gorodetsky, A.E. Yachmenev et al. "Enhanced terahertz emission from strain-induced InGaAs/InAlAs superlattices". J. Appl. Phys., 125(15), 151605, 2019.
7. D.V. Lavrukhin, A.E. Yachmenev, Yu.G. Goncharov et al. "Strain-induced InGaAs-based photoconductive terahertz antenna detector". IEEE. Trans. THz. Sci. Technol., 11(4), 417, 2021.

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Speaker

Denis Lavrukhin
Prokhorov General Physics Institute of the Russian Academy of Sciences
Russia

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