Room-temperature THz photon detection via nonlinear upconversion with 2% full-system efficiency

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Hauptverfasser: Vishnuradhan, Aswin, Cui, Wei, Heydarian, Hesam, Yalavarthi, Eeswar Kumar, Couture, Nicolas, Villeneuve, Alain, Gamouras, Angela, Ménard, Jean-Michel
Format: Preprint
Veröffentlicht: 2026
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author Vishnuradhan, Aswin
Cui, Wei
Heydarian, Hesam
Yalavarthi, Eeswar Kumar
Couture, Nicolas
Villeneuve, Alain
Gamouras, Angela
Ménard, Jean-Michel
author_facet Vishnuradhan, Aswin
Cui, Wei
Heydarian, Hesam
Yalavarthi, Eeswar Kumar
Couture, Nicolas
Villeneuve, Alain
Gamouras, Angela
Ménard, Jean-Michel
contents Sensitive detection of terahertz (THz) radiation is fundamental to progress in spectroscopy, advanced wireless communication, and the realization of emerging quantum technologies. However, the intrinsically low photon energies in the THz range combined with thermal background radiation tend to constrain detector performance when operating at ambient temperatures. Here, we demonstrate efficient room-temperature THz detection based on nonlinear upconversion in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) to resolve frequencies from 1 to 7.5 THz. The system encompassing spectral filters and a single-photon counter achieves an overall detection efficiency of 2% for sum-frequency generated photons. This enables the detection of a train of 50 000 terahertz pulses carrying, on average, fewer than 0.04 photons per pulse, with a signal-to-noise ratio of unity. At a higher flux, when ~60 photons per pulse impinge on the BNA crystal, the per-pulse detection probability reaches 50%. After accounting for loss mechanisms in the setup, the nonlinear THz-to-near-infrared conversion efficiency in BNA exceeds 75%. These results demonstrate the feasibility of quantum experiments relying on single-photon-level THz detection via upconversion in nonlinear crystals in ambient conditions.
format Preprint
id arxiv_https___arxiv_org_abs_2605_20424
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Room-temperature THz photon detection via nonlinear upconversion with 2% full-system efficiency
Vishnuradhan, Aswin
Cui, Wei
Heydarian, Hesam
Yalavarthi, Eeswar Kumar
Couture, Nicolas
Villeneuve, Alain
Gamouras, Angela
Ménard, Jean-Michel
Optics
Sensitive detection of terahertz (THz) radiation is fundamental to progress in spectroscopy, advanced wireless communication, and the realization of emerging quantum technologies. However, the intrinsically low photon energies in the THz range combined with thermal background radiation tend to constrain detector performance when operating at ambient temperatures. Here, we demonstrate efficient room-temperature THz detection based on nonlinear upconversion in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) to resolve frequencies from 1 to 7.5 THz. The system encompassing spectral filters and a single-photon counter achieves an overall detection efficiency of 2% for sum-frequency generated photons. This enables the detection of a train of 50 000 terahertz pulses carrying, on average, fewer than 0.04 photons per pulse, with a signal-to-noise ratio of unity. At a higher flux, when ~60 photons per pulse impinge on the BNA crystal, the per-pulse detection probability reaches 50%. After accounting for loss mechanisms in the setup, the nonlinear THz-to-near-infrared conversion efficiency in BNA exceeds 75%. These results demonstrate the feasibility of quantum experiments relying on single-photon-level THz detection via upconversion in nonlinear crystals in ambient conditions.
title Room-temperature THz photon detection via nonlinear upconversion with 2% full-system efficiency
topic Optics
url https://arxiv.org/abs/2605.20424