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Single-crystal diamond possesses exceptional physical and optical properties, rendering it an ideal platform for integrated quantum optics. The direct integration of broadband-sensitive and high-performance single-photon detectors on diamond holds significant implications for the realization of integrated diamond quantum optical circuits. In this study, we polished the diamond surface with RMS (root mean square) below 0.6 nm suitable for the deposition and patterning of NbN thin films through ion beam etching. Subsequently, we fabricated superconducting nanowire single-photon detectors directly on the polished diamond substrates and characterized for their electrical and optical properties. The NbN-SNSPD exhibited a high critical current density (2 MA cm−2), a saturated quantum efficiency (QE) below 2.5 K, and a maximum value of QE up to 88% at 4 K. These findings offer a promising solution for fully integrated quantum optical chips on single-crystal diamond substrates. [ABSTRACT FROM AUTHOR]

A large-area single-photon detector with a high maximum count rate (MCR) is expected by LiDAR application for a large dynamic range and high coupling efficiency. Superconducting nanowire single-photon detectors (SNSPDs) are very competitive for high quantum efficiency at near infrared wavelengths. However, it is a great challenge to balance the efficiency, area, and MCR of SNSPDs due to the long superconducting nanowire architecture. In this article, we design a large-area SNSPD with a high MCR for LiDAR applications. The SNSPD has four independent channels, and each of them is composed of four parallel nanowires. The photosensitive area has a diameter of 60 μm and can be coupled with a 200-μm multimode fiber through a lens. At the same time, we analyze the origin of the detector latching under high count rates and propose a discharge acceleration circuit to alleviate it. In the experiment, an MCR of 147 Mcps is achieved in this SNSPD. The product of area and MCR for each channel of this SNSPD is twice higher than previously reported results. We highlight that this work is of great significance for the application of SNSPD in LiDAR. [ABSTRACT FROM AUTHOR]

Superconducting nanowire single-photon detectors (SNSPDs) with high detection efficiency have played significant role in numerous applications for photon detection from visible light to mid-infrared band. However, it is still a challenge to easily promote the sensitivity of SNSPD without compromising its other performance. We report a method to improve the detection sensitivity of devices via suspended SiO2 membrane, and the intrinsic detection efficiency is significantly enhanced from 78% to 100% for a 1550 nm wavelength. The electro-thermal simulation and hotspot relaxation time measurement indicate that a suspended SiO2 membrane can significantly decrease the cooling efficiency between the hotspot and the substrate, and the relaxation time is enlarged twice than before. Meanwhile, we note that the proposed method does not affect other properties of devices, such as dark count rate, detection speed, and timing jitter. Because the thermal dissipation process can be controlled continuously (by varying the size of the suspended area), the proposed method may also help to obtain a deeper understanding of the thermal diffusion and detection process of SNSPDs. [ABSTRACT FROM AUTHOR]

Although many multiplexed arrays of a superconducting nanowire single-photon detector (SNSPD) have been reported, it is still a major challenge to develop pixel-level readout arrays with high efficiency, parallel detection, and fast processing for real-time imaging. Here, we report a SNSPD array with inductor-shaping pulses for approaching the pixel-level readout. Optimized inductors are introduced to shape the output pulses of each pixel, and the response pulses of all pixels are synthesized in a series-connected structure. Then, the on/off states of all pixels can be encoded to the widths, amplitudes, and areas of the output pulses by the single-channel readout. This proposal is verified by a 4-pixel SNSPD array and a 16-pixel SNSPD array. It shows that the array not only inherits the features of the single-pixel SNSPD, such as photosensitive area, filling factor, quantum efficiency, and dark count rate, but also implements parallel operation of all pixels, which is always confused in traditional multiplexed SNSPD arrays. At the same time, the single-channel readout simplifies the system, and the serial digital signal converted from the shaped pulse enabled an easy and fast readout process, paving the way for high performance and real-time imaging. [ABSTRACT FROM AUTHOR]

As a competitive technology, the superconducting nanowire single-photon detector (SNSPD) is developing from a single-pixel to array architecture; however, it is a major challenge for reading array detectors. We propose an encodable trigger through the thermal coupling of two adjacent superconducting nanowires, which can read a current pulse with microampere amplitude and code the current pulses of different positions with different output resistances simultaneously. At the same time, the influence of external noise on superconducting devices can be avoided for isolated circuits. As a demonstration, the response pulses of a 4-pixel SNSPD are read using this trigger in the absence of an amplifier, and the photon flux distribution of different pixels is accurately reconstructed, where the total power consumption is approximately 0.8 μW. The superconducting trigger is promising for application in integrated superconducting electronics and quantum optics in the future. [ABSTRACT FROM AUTHOR]

This document is an erratum for an article titled "Superconducting nanowire single-photon detectors with saturated quantum efficiency at 1550 nm on single-crystal diamond substrates" published in Applied Physics Letters. The authors have identified two errors in the original article: an incorrect AFM scanning image in Figure 1 and a marked incorrect size in Figure 4(b). The corrected figures are provided in the erratum. The errors do not affect any other results, discussions, or conclusions in the original article. [Extracted from the article]

In this Letter, we report on pattern engineering in superconducting microstrips to achieve a fast and efficient detection of a single-photon over a large detection area. The proposed detector is composed of hole-patterned superconductor microstrips fabricated with a 5-nm-thick amorphous molybdenum silicide film. It exhibits a saturated internal detection efficiency at 1550 nm with a negligible dark count rate and a recovery time of 9 ns with a large detection area (50 × 50 μm2). The simulation reveals that the holes patterned in the superconductor microstrip stimulate the nucleation of the vortex, which constitutes a major key to achieving the efficient detection of photons. This work paves the way for the facile and prolonged regulation of vortex nucleation in superconductors, which shows promise for developing high-performance large-area superconductor single-photon detectors. [ABSTRACT FROM AUTHOR]

In this Letter, we report on a device with which to resolve photon numbers and positions simultaneously, using single-channel readout from superconducting nanowire single-photon detectors (SNSPDs). The nanowires in the SNSPDs are connected in series with parallel resistors for producing response pulses with different amplitudes, whose values obey a distribution of 1:2:4:,..,2n-1. In single-photon detection, a saturated counting rate is obtained at a low dark count rate (<10 cps). Furthermore, we observed 16 output modes corresponding one-to-one with 16 states (15 photon responses + 1 state without photons) in multiphoton mode. This structure not only inherits the advantages of high quantum efficiency and low dark count rate of traditional SNSPD, but also realizes the resolution of photon position and number simultaneously without complicated optical system. Thus, this proposal offers a promising platform for realizing scalable and practical quantum information chips. [ABSTRACT FROM AUTHOR]

Terahertz (THz) photonic waveguides are of great importance in THz integrated technology, especially for versatile signal processing. However, in THz photonics, very few fundamental "building blocks" equivalent to those used in muti-functional electronics circuits exist. This study proposes a photonics-inspired micro-ring whispering gallery mode resonator (WGMR) waveguide with a standard waveguide-compatible package on silicon platform. A gradual taper is integrated on the same chip to improve the coupling efficiency and reduce transmission loss. The packaged WGMR waveguide with an operating range of 0.360 to 0.440 THz had a maximum measured extinction ratio of 32 dB at 0.390 THz, with a Q factor of 385 and an insertion loss of 2.6 dB. The compact and standard waveguide-compatible packaged WGMR can easily be integrated into practical terahertz application systems for THz signal processing and as a tool for the study of fundamental THz science. [ABSTRACT FROM AUTHOR]