Experimental setup and protocols to characterize the in-house THz photoconductive antennas

Abstract

Photoconductive antennas (PCAs) play a crucial role in the generation and detection of THz radiation, making them vital components in various applications, including THz time-domain dielectric spectroscopy and THz multispectral imaging [1,2]. PCAs can efficiently work at room temperature demonstrating a broadband spectrum up to 0.1-5.0 THz with a perfect dynamic range, i.e. signal-to-noise ratio exceeding even 100 dB [3]. One can note that the features of these antennas, especially the bandwidth and radiated power, are highly dependent on their operational mode, which requires precise tuning.

We report our experimental setup and protocols developed to characterize in-house THz photoconductive antennas. The revealed limiting characteristics are subsequently used as reference values when using our PCAs in practical applications. Setup includes a video camera for real-time monitoring size and position of the laser excitation spot relative to PCA electrodes. In parallel, we continuously measure the photocurrent, preventing overheating and subsequent thermal breakdown of the PCA [4], thereby providing complete information on the operating mode of the PCA.

Examples of measured THz spectra obtained for various conditions of laser excitation and optical/THz alignment of PCA-emitter are given, showing how changes in these parameters can affect the spectral characteristics and overall efficiency of the time-domain spectrometer. Additionally, we compared such results with our measurements of original large-area THz emitters [5]. The results provide valuable insight into optimization of THz PCAs operation mode, contributing to a broader understanding and enhancement of THz technology.

1. D.S. Ponomarev, A.E. Yachmenev, D.V. Lavrukhin et al. “Optical-to-terahertz switches: state of the art and new opportunities for multispectral imaging”. Uspekhi Fizicheskih Nauk, 194(1), 2–22, 2024.
2. E. Castro-Camus, M. Alfaro. “Photoconductive devices for terahertz pulsed spectroscopy: a review [Invited]”. Photonics Research, 4(3), A36, 2016.
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. M.Welsch, A. Singh, S.Winnerl. “High–Bias–Field Operation of GaAs Photoconductive Terahertz Emitters”. J Infrared Milli. Terahz Waves, 42, 537–546, (2021).
5. N. V. Zenchenko, D. V. Lavrukhin, R.R. Galiev et al. “Enhanced terahertz emission in a large-area photoconductive antenna through an array of tightly packed sapphire fibers”. Applied Physics Letters, 124(12), 1–5, 2024.

Speaker

Artem E. Zubov
Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow
Russia

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