Over the past decade, multi-element superconducting nanowire single-photon detectors (SNSPDs) have emerged as the leading single-photon detection technology due to their exceptional system detection efficiency (SDE), ultrahigh timing precision, negligible dark counts, etc. However, achieving these performances with a \textit{single-element} SNSPD has been an outstanding challenge due to a fundamental trade-off: a large active area is necessary for high SDE, while a smaller area is crucial for higher photon count rates, lower dark counts, and lower jitter. Here, we introduce an all-dielectric cryogenic metalens integrated with a single-element SNSPD to achieve high SDE with a smaller active area. Furthermore, we leverage a bifunctional metalens to demonstrate polarization-resolved photodetection at the telecommunication wavelength theoretically. Integrating multifunctional cryogenic metaurfaces with the state-of-the-art SNSPDs may enable novel capabilities with reduced size, weight, power, cost, and cooling (SWaP-C$^{2}$) requirements.
Over the past decade, multi-element superconducting nanowire single-photon detectors (SNSPDs) have emerged as the leading single-photon detection technology due to their exceptional system detection efficiency (SDE), ultrahigh timing precision, negligible dark counts, etc. However, achieving these performances with a \textit{single-element} SNSPD has been an outstanding challenge due to a fundamental trade-off: a large active area is necessary for high SDE, while a smaller area is crucial for higher photon count rates, lower dark counts, and lower jitter. Here, we introduce an all-dielectric cryogenic metalens integrated with a single-element SNSPD to achieve high SDE with a smaller active area. Furthermore, we leverage a bifunctional metalens to demonstrate polarization-resolved photodetection at the telecommunication wavelength theoretically. Integrating multifunctional cryogenic metaurfaces with the state-of-the-art SNSPDs may enable novel capabilities with reduced size, weight, power, cost, and cooling (SWaP-C2) requirements.
ABSTRACT Over the past decade, multielement superconducting nanowire single‐photon detectors (SNSPDs) have emerged as the leading single‐photon detection technology due to their exceptional system detection efficiency (SDE), ultrahigh timing precision, and negligible dark counts. However, achieving these performances with a single‐element SNSPD has been an outstanding challenge due to a fundamental trade‐off: A large active area is necessary for high SDE, whereas a smaller area is crucial for higher photon count rates, lower dark counts, and lower jitter. Here, we introduce a dielectric cryogenic metalens integrated with a single‐element SNSPD to achieve high SDE with a smaller active area. We report a 77‐fold enhancement in the SDE of a metalensed SNSPD with a 5 m 5 m active area, compared with an identical reference SNSPD without a metalens, using a moderately sized 60 m 60 m metalens. Next, we theoretically demonstrate polarization‐resolved photodetection at the telecommunication wavelength using a bifunctional metalens. We achieve a cross‐detection probability of 2 between metalensed SNSPDs spaced at 10 m under illumination with x ‐ and y ‐polarized light. Integrating a multifunctional cryogenic metasurface with the state‐of‐the‐art SNSPDs may enable novel capabilities with reduced size, weight, power, cost, and cooling (SWaP‐) requirements.
Superconducting detectors capable of registering single light quanta - single photons - are highly sought after in a host of emerging 21st century technologies [1]. Superconducting nanowire single-photon detectors (SNSPDs or SSPDs) [2] operating in the telecommunication wavelength range outperform conventional semiconductor detectors in the following metrics: dark count rate, system detection efficiency (SDE), photon counting rate and timing jitter [3, 4, 5, 6]. SNSPDs have been deployed in many important emerging photon-counting applications including single photon LiDAR [7, 8], quantum key distribution [9, 10], optical quantum computing [11], life sciences [12, 13], fibre sensing [14, 15], exoplanet spectroscopy [16] and free space optical communication [17].
Multimode fiber (MMF)-coupled superconducting nanowire single-photon detectors (SNSPDs) are critical for free-space quantum communication and sensing, yet their performance is severely limited by polarization-dependent detection efficiency and high dark count rate (DCR) arising from thermal photons. Here, we present a transformative solution that addresses both challenges simultaneously. We demonstrate a polarization-insensitive SNSPD based on a dielectric-compensated bilayer nanowire structure, achieving a system detection efficiency (SDE) of 88% at 1.5 μm with a DCR of ∼4.8×10 4 cps for MMF-coupled signals. To mitigate the elevated thermal noise inherent to multimode coupling, we integrate a compact, dual-stage on-fiber filter with a suppression ratio exceeding 60 dB. The packaged device delivers an SDE of 81% with a DCR of only 4 cps, corresponding to an over 11,000-fold SNR enhancement relative to the unfiltered MMF-coupled configuration.
Ever since superconducting nanowire single-photon detectors (SNSPDs or SSPDs) were demonstrated, they have attracted a considerable attention due to the detectors’ promising performance that includes high detection efficiency (DE), low dark count rate (DCR), broadband sensitivity, and low timing jitter. The system detection efficiency (SDE) has been improved to be over 90% with a wavelength of 1550 nm in a fiber-coupled system by embedding the SNSPD in optical cavities. However, the implementation of optical cavity usually reduces the bandwidth of SNSPDs. As a result, there are some recent works on increasing the bandwidth of SNSPD. Furthermore, the size of the active area of meandered nanowires has to be compatible with the core size of an optical fiber such that good optical coupling can be achieved; this setup requires a long nanowire with a large kinetic inductance, thus resulting in a small counting rate and a large timing jitter, particularly for multi-mode fiber-coupled devices. Nevertheless, a particularly impressive waveguide-coupled SNSPD has been developed in recent years. By placing an SNSPD atop an optical waveguide that has been fabricated on various substrate materials, photons propagating in the waveguide have been found to be evanescently absorbed by nanowires that are only a few tens of microns long. The on-chip DE of this device has been estimated to be over 90%, thus indicating that it has both high absorptance and high intrinsic DE. If the waveguide and the nanowire are correctly dimensioned, the absorptance of this device can reach over 90% for a wavelength range of more than 700 nm. Furthermore, the length of the nanowire is shorter than that of the fiber-coupled SNSPD, thus leading to a higher count rate and lower timing jitter (~18 ps). However, unsatisfactory coupling losses between the optical fiber and the waveguide in such devices can decrease its SDE (~10%), thus limiting its applicability to quantum photonic integrated circuits (QPIC). Recently, we proposed a type of SNSPD that was coupled with microfibers (MFs), and simulations for this SNSPD indicated that its absorption would be as high as 90%. Microfibers and nanofibers, tapered adiabatically from standard fibers, with diameters close to or smaller than the wavelength of the guided light were demonstrated to have low transmittance losses by Tong et al. in 2003. MFs have been shown to have many interesting properties, such as strong evanescent fields, tight optical confinement, wideband abilities, and small masses; these properties are appealing for applications such as optical sensing and coupling. MFs also provide seamless connections with high transmittance from standard fibers; therefore, MF-coupled SNSPDs can achieve both high SDEs and wideband compatibility. We proposed and demonstrated the MF-coupled SNSPDs successfully. The simulation results indicate that with optimal device structure, the optical absorption with efficiency < 90% can be realized over a wavelength range of 350 nm to 2150 nm. The fabricated MF-coupled SNSPD, shows unparalleled broadband system detection efficiencies (SDEs) of more than 50% from 630 nm to 1500 nm. The SDEs reach 66% at 785 nm and 45% at 1550 nm. These results pave the way for ultra-broadband weak light detection with quantum-limit sensitivity.
Superconducting nanowire single-photon detectors (SNSPDs) are an enabling technology for myriad quantum-optics experiments that require high-efficiency detection, large count rates, and precise timing resolution. The system detection efficiencies (SDEs) for fiber-coupled SNSPDs have fallen short of theoretical predictions of near unity by at least 7%, with the discrepancy being attributed to scattering, material absorption, and other SNSPD dynamics. We optimize the design and fabrication of an all-dielectric layered stack and fiber coupling package in order to achieve 98.0 ± 0.5 % SDE, measured for single-mode-fiber guided photons derived from a highly attenuated 1550 nm continuous-wave laser. This enforces a smaller bound on the scattering and absorption losses in such systems and opens the use of SNSPDs for scenarios that demand high-SDE for throughput and fidelity.
Superconducting Nanowire Single Photon Detectors (SNSPDs) excel at a wide variety of performance criteria for single photon counting. They combine unprecedented high detection efficiency, high timing resolution, high count rates, low intrinsic dark count rates, and are sensitive to ultraviolet through mid-infrared single-photons. At JPL, we are working on several projects to push the performance limits of SNSPDs to achieve higher maximum count rates, larger active areas, higher timing resolution, and a wider spectral range. Our recent advances enable new applications for dark matter detection, imaging, and space-to-ground communication and provide insight into the fundamental physics of single-photon detection in superconducting nanowires.