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arXiv:2412.09462

Near-single-photon atto-watt detection at mid-infrared wavelengths by a room-temperature balanced heterodyne set-up

Danièle Palaferri, Lorenzo Mancini, Chiara Vecchi, Leonardo Daga, Pierfrancesco Ulpiani, Massimiliano Proietti, Carlo Liorni, Massimiliano Dispenza, Francesco Cappelli, Paolo De Natale, Simone Borri

Published Feb 5, 2025• 1 citation
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Abstract

Abstract Single photon detection is the underpinning technology for quantum communication and quantum sensing applications. At visible and near-infrared wavelengths, single-photon-detectors (SPDs) underwent a significant development in the past two decades, with the commercialization of SPADs and superconducting detectors. At longer wavelengths, in the mid-infrared range (4-11µm), given the reduced scattering and favourable transparent atmospheric windows, there is an interest in developing quantum earth-satellites-links and quantum imaging for noisy environments or large-distance telescopes. Still, SPD-level mid-infrared devices have been rarely reported in the state-of-the-art (superconductors, single-electron-transistors or avalanche-photodiodes) and, crucially, all operating at cryogenic temperatures. Here, we demonstrate a room-temperature detection system operating at 4.6µm-wavelength with a sensitivity-level of atto-watt optical power, corresponding to few tens of mid-infrared photons. This result was obtained by exploiting a pair of commercially available photodetectors within two balanced-heterodyne-detection setups: one involving a quantum-cascade-laser (QCL) and an acousto-optic-modulator (AOM) and the other one including two QCLs with mutual coherence ensured by a phase-lock-loop (PLL). Our work not only validates a viable method to detect ultra-low-intensity signals, but is also potentially scalable to the entire wavelength range already accessible by mature QCL technology, unfolding - for the first time - quantum applications at mid- and long-wave-infrared-radiation.

DOI
10.21203/rs.3.rs-5850487/v1

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Abstract Single photon detection is the underpinning technology for quantum communication and quantum sensing applications. At visible and near-infrared wavelengths, single-photon-detectors (SPDs) underwent a significant development in the past two decades, with the commercialization of SPADs and superconducting detectors. At longer wavelengths, in the mid-infrared range (4-11µm), given the reduced scattering and favourable transparent atmospheric windows, there is an interest in developing quantum earth-satellites-links and quantum imaging for noisy environments or large-distance telescopes. Still, SPD-level mid-infrared devices have been rarely reported in the state-of-the-art (superconductors, single-electron-transistors or avalanche-photodiodes) and, crucially, all operating at cryogenic temperatures. Here, we demonstrate a room-temperature detection system operating at 4.6µm-wavelength with a sensitivity-level of atto-watt optical power, corresponding to few tens of mid-infrared photons. This result was obtained by exploiting a pair of commercially available photodetectors within two balanced-heterodyne-detection setups: one involving a quantum-cascade-laser (QCL) and an acousto-optic-modulator (AOM) and the other one including two QCLs with mutual coherence ensured by a phase-lock-loop (PLL). Our work not only validates a viable method to detect ultra-low-intensity signals, but is also potentially scalable to the entire wavelength range already accessible by mature QCL technology, unfolding - for the first time - quantum applications at mid- and long-wave-infrared-radiation.
Abstract Balanced heterodyne detection (BHD) is a key technology at visible and near‐infrared wavelengths for quantum communication and quantum sensing applications based on coherent read‐out schemes. Extending BHD at mid‐infrared wavelengths (4–11 µm), given the reduced scattering and favourable transparent atmospheric windows, could enable robust earth‐satellite links and few‐photon imaging in high‐noise environments. Currently, quantum applications at these wavelengths are hindered by the lack of high‐sensitivity, room‐temperature photoreceivers; moreover, mid‐infrared single‐photon‐detectors reported to date (superconductors, single‐electron‐transistors, or avalanche‐photodiodes) require cryogenic operation, limiting practicality. Here, a room‐temperature BHD system operating at 4.6 µm‐wavelength with atto‐watt sensitivity level, corresponding to a few tens of photons per second, is demonstrated. This result is obtained by selecting commercially available photodetectors with the highest detectivity and exploiting two heterodyne setups ‐one involving a single quantum‐cascade‐laser (QCL) and an acousto‐optic‐modulator (AOM), and the other one including two QCLs with mutual coherence ensured by a phase‐locked‐loop. Combining a sufficiently high local oscillator (LO) power and the high phase‐coherence between signal and LO is crucial to push the system noise‐equivalent‐power (NEP) to values approaching the shot‐noise‐limit, as confirmed by few‐photons interferometry measurements. This work not only validates viable methods to detect ultra‐low‐intensity signals, but is also potentially scalable to the entire wavelength range already accessible by state‐of‐the‐art mid‐infrared technology.
Quantum measurements using single-photon detectors are opening interesting new perspectives in diverse fields such as remote sensing, quantum cryptography and quantum computing. A particularly demanding class of applications relies on the simultaneous detection of correlated single photons. In the visible and near infrared wavelength ranges suitable single-photon detectors do exist. However, low detector quantum efficiency or excessive noise has hampered their mid-infrared (MIR) counterpart. Fast and highly efficient single-photon detectors are thus highly sought after for MIR applications. Here we pave the way to quantum measurements in the MIR by the demonstration of a room temperature coincidence measurement with non-degenerate twin photons at about 3.1 μm. The experiment is based on the spectral translation of MIR radiation into the visible region, by means of efficient up-converter modules. The up-converted pairs are then detected with low-noise silicon avalanche photodiodes without the need for cryogenic cooling.
Extending single-photon detection capabilities into the mid- infrared is expected to have far-reaching implications for long-wavelength quantum optics, quantum and free-space communication, astronomy, environmental monitoring, and fundamental molecular sciences. We showcase the development of short-wave infrared (2.2-2.3 µm) and mid- wave infrared (3.0 µm) superconducting nanowire single-photon detectors (SNSPDs). In both wavelength ranges, we venture beyond state-of-the-art and achieve the best-reported system detection efficiencies and specific detectivity. We discuss the challenges in cryogenics, optics, and SNSPD design and use our mid-infrared single-photon detection to characterize emerging materials platforms and quantum emitters in a previously unattainable manner.
Single-photon counting has become an essential tool in quantum optics experiments, as well as remote sensing and life science applications. However conventional technologies such as single-photon avalanche diodes, as well as the availability of standard telecom optical components, has limited much of this work to the near infrared/telecom wavelength range. Superconducting nanowire single photon detectors (SNSPDs) have emerged in recent years as the gold standard in photon counting applications due to their low dark count rates, fast timing resolution and high efficiency [1]. SNSPDs have also demonstrated photon counting efficiency out to much greater wavelengths which enables us to explore new experimental possibilities in the mid-infrared [2]. In this work we design and fabricate mid-infrared SNSPDs and deploy them in a variety of photon counting experiments [3,4]. The devices are based on a NbTiN superconducting film integrated into an optical cavity to enhance absorption in the mid-infrared. We characterise these devices using an optical parametric oscillator, tuneable between 1.5 m and 4.2 m. We then deploy these in a proof-of-principle tabletop light detection and ranging (LIDAR) experiment at 2.3 m. LIDAR in the mid-infrared is attractive due to spectral regions of low atmospheric absorption and reduced solar background photon flux, when compared to telecom wavelengths. We also present results from a photon-pair source operating at 2 m. This is a key resource for extending quantum optics and quantum secure communications to the mid infrared domain. Pairs are generated using a custom lithium niobate crystal and detected using SNSPDs. We demonstrate two-photon interference and polarisation entanglement of the photon pairs at 2 m. This work opens the pathway to future development of quantum optics and quantum technologies in the mid-infrared spectral region. References [1] Gol’tsman et al Applied Physics Letters 79 705 (2001) [2] Marisli et al Nano Letters 12 (9) 4799 (2012) [3] G. G. Taylor et al Optics Express 26 (27) 38147 (2018) [4] S. Prabhakar et al Science Advances 6 (13) eaay5195 (2019)
Extending single-photon detection capabilities into the mid- infrared is expected to have far-reaching implications for long-wavelength quantum optics, quantum and free-space communication, astronomy, environmental monitoring, and fundamental molecular sciences. We showcase the development of short-wave infrared (2.2-2.3 µm) and mid- wave infrared (3.0 µm) superconducting nanowire single-photon detectors (SNSPDs). In both wavelength ranges, we venture beyond state-of-the-art and achieve the best-reported system detection efficiencies and specific detectivity. We discuss the challenges in cryogenics, optics, and SNSPD design and use our mid-infrared single-photon detection to characterize emerging materials platforms and quantum emitters in a previously unattainable manner.
Single-photon detectors (SPDs) are the most sensitive instruments for light detection. In the near-infrared range, SPDs based on III–V compound semiconductor avalanche photodiodes have been extensively used during the past two decades for diverse applications due to their advantages in practicality including small size, low cost and easy operation. In the past decade, the rapid developments and increasing demands in quantum information science have served as key drivers to improve the device performance of single-photon avalanche diodes and to invent new avalanche quenching techniques. This Review aims to introduce the technology advances of InGaAs/InP single-photon detector systems in the telecom wavelengths and the relevant quantum communication applications, and particularly to highlight recent emerging techniques such as high-frequency gating at GHz rates and free-running operation using negative-feedback avalanche diodes. Future perspectives of both the devices and quenching techniques are summarized. Recent progress in single-photon detectors for quantum communication based on III–V compound semiconductor avalanche photodiodes is reviewed. Specifically, Jun Zhang and Jian-Wei Pan at the University of Science and Technology of China and their colleagues in the USA and Switzerland introduce technological advances for InGaAs/InP single-photon detector systems in the telecommunication band along with their associated applications in quantum communication. III–V single-photon avalanche diodes are the most practical tools available for detecting ultraweak near-infrared light. The scientists overview important parameters for evaluating the performance of detector systems based on single-photon avalanche diodes and describe the experimental characterization of these parameters. They also consider emerging techniques, including high-frequency gating at gigahertz rates and free-running operation using negative-feedback avalanche diodes. Finally, the future prospects of these devices are considered.