A multispectral superconducting nanowire single-photon detector (SNSPD) that is sensitive to different incident photon wavelength bands, is proposed. The SNSPD consists of a distributed Bragg reflector (DBR), a gold mirror, and two regions employing four NbN nanowire meander layers. Using the DBR, both as a filter and a reflector, creates two distinct detection bands. The first detection band has a peak absorptance of 0.792 at a wavelength of 1164 nm, while the second band has a total absorptance of >0.70 in the wavelength range 1440 to 2000 nm. The design of the proposed SNSPD can be tuned to provide sensitivity to different wavelength bands. While conventional SNSPDs do not typically provide photon wavelength sensitivity, the band-selection design proposed in this work opens up its potential applications for future quantum communication technology.
A multispectral superconducting nanowire single-photon detector (SNSPD) that is sensitive to different incident photon wavelength bands, is proposed. The SNSPD consists of a distributed Bragg reflector (DBR), a gold mirror, and two regions employing four NbN nanowire meander layers. Using the DBR, both as a filter and a reflector, creates two distinct detection bands. The first detection band has a peak absorptance of 0.792 at a wavelength of 1164 nm, while the second band has a total absorptance of >0.70 in the wavelength range 1440 to 2000 nm. The design of the proposed SNSPD can be tuned to provide sensitivity to different wavelength bands. While conventional SNSPDs do not typically provide photon wavelength sensitivity, the band-selection design proposed in this work opens up its potential applications for future quantum communication technology.
Abstract The multispectral and polarization-sensitive detection of superconducting nanowire single photon detectors (SNSPDs) have been identified in applications, such as quantum information processing and polarimetric imaging systems. Distributed Bragg reflectors (DBRs) demonstrate exceptional wavelength-selective reflectivity, and subwavelength gratings (SWGs) exhibit the ability to separate different polarized light. In this paper, a multispectral and polarization-sensitive SNSPD design is proposed by combining DBRs and SWGs. In the design, the NbN nanowires are positioned on two DBR stacks with respective central wavelengths of 1400 nm and 930 nm, followed by integration of Si-Al composite gratings onto the surface layer. Numerical simulation results show that, setting the fill factor at 0.5, the polarization sensitivity of the SNSPD is ∼0.98, with absorption efficiencies of ∼95%, ∼92%, and ∼94% at wavelengths of 1064 nm, 1310 nm, and 1550 nm, respectively. The design proposed in this work could facilitate the development of high-performance SNSPDs, potentially advancing their applications in multispectral polarization imaging and quantum communication systems.
In this work, we report multispectral superconducting nanowire single photon detectors (SNSPDs) that can simultaneously detect single photons at multiple wavelengths with high efficiency. The superconducting nanowires are fabricated on an all-dielectric mirror consisting of two quarter-wave stack reflectors with separated central wavelengths. The unique optical structure results in serially coupled optical cavities, leading to multiple resonant absorption bands that are utilized for high-efficiency single photon detection. The fabricated detector shows system detection efficiencies of >80% at the three target wavelengths of 1550 nm, 1310 nm, and 1064 nm. The multispectral detector may eliminate the need for multiple SNSPDs for different wavelengths in a system, potentially resulting in a reduction in size, weight, and power, as well as in the cost of the overall detection system. The detector may also find interesting use for applications such as multispectral ranging or imaging.
Superconducting nanowire single-photon detectors (SNSPDs) struggle to balance high system detection efficiency (SDE) and low polarization dependence. This work proposes a co-design of the NbN films, α -Si anti-reflection coating (ARC), and SiO 2 /Ta 2 O 5 distributed Bragg reflector (DBR) to reduce the polarization-dependent optical response of the nanowires. Simulations based on rigorous coupled-wave analysis (RCWA) and the finite-element method show absorptance above 99% for both transverse-electric (TE) and transverse-magnetic (TM) polarizations and absorptance above 90% over the wavelength range from 1530 to 1640 nm. Experimentally, the device achieves 97% SDE at 1530 nm (polarization sensitivity, PS = 1.1), PS < 1.3 over 1490–1640 nm, 39.5 ns recovery time, and 63.5 ps timing jitter. Retaining a conventional single-layer meander nanowire geometry, this design unifies high efficiency and polarization insensitivity, advancing SNSPD applications in quantum communications, free-space links, and single-photon imaging.
We propose a superconducting nanowire single photon detector (SNSPD) that can work efficiently at two target wavelengths and has a significant improvement in the counting rate due to the low-filling-factor nanowires in the silicon slots and the silver reflector. Numerical simulations show that the absorption efficiency can be over 90% at a single wavelength, whether the incident light wavelength is 1550 nm or 1064 nm, and over 80% when the SNSPD is designed to work at both wavelengths. In addition, the reset time is about 24% of the conventional SNSPDs. Our work presents a design for fabricating faster, larger-area, and multispectral SNSPDs with a high efficiency, which can be applied in applications such as quantum optics communication and multiwavelength sensing.
Abstract This paper presents the development of a superconducting nanowire single-photon detector (SNSPD) integrated into a distributed Bragg reflector (DBR) with a design center wavelength of 830 nm and a bandwidth of 200 nm. This SNSPD is made of a superconducting niobium nitride (NbN) thin film that is produced using plasma-enhanced atomic layer deposition. The DBR is made of 15 alternating layers of silicon nitride and silicon oxide that are produced through plasma-enhanced chemical vapor deposition. The reflection efficiency of the mirror is 90% at a wavelength of 830 nm. For sufficient optical coupling, an optical micro-connector optimized for multimode or single-mode optical fibers with a diameter of 128 μm was formed using two-photon polymerization techniques. The niobium nitride film was deposited onto the DBR surface in-situ in two separate reactors connected by a vacuum transfer. The in-situ technique of deposition of a superconducting niobium nitride film and a DBR has allowed achieving a system detection efficiency of 90% at a wavelength of 830 nm and a dark count rate of 10 s−1 at a temperature of 2.5 K. Additionally, the detector jitter was 50 ps.
Single photon detection advanced rapidly in the last decade. The superconducting nanowire single-photon detector (SNSPD) is an emerging technology, which offers low dark count rates, broadband sensitivity from visible to mid-infrared wavelengths and very high quantum efficiency. All these features are appealing for future emerging applications in remote gas sensing, quantum key distribution and quantum information processing. By enclosing the detector in an optical cavity, tuned to the operating wavelength, the total system detection of the SNSPD is improved. Based on the cavity design, the detector absorption is boosted at the desired experimental wavelength. Devices have been fabricated and tested, in this thesis, with enhanced detection efficiency at near-infrared, infrared and mid-infrared wavelengths. NbTiN detectors fabricated on Ta2O5 / SiO2 distributed Bragg reflectors (DBR) for front-side coupling exhibit a system detection efficiency of ≈ 90% at λ = 940 nm for the best device measured. SNSPDs were also fabricated in NbTiN on metallic mirrors for back-side coupling for 1550 and 2333 nm experimental wavelengths. The first design exhibited a system detection efficiency of ≈ 84.5%, at λ = 1550 nm for the best device measured. The second exhibited low system detection efficiency since the device suffered from unexpectedly high dark count rate mainly due to blackbody radiation at 2.2 K. However, it was possible to measure the timing jitter of this device at 350 mK indicating a FWHM of 84 ps. Another technique to improve the total system detection efficiency of the SNSPD, is by fabricating a hairpin-shaped nanowire atop a single mode waveguide. In this design, photons travel through the waveguide and via evanescent coupling are absorbed in the nanowire. These SNSPD devices have been designed to thread along single mode Si ridge waveguides using a hairpin-shaped nanowire structure, which offers enhanced coupling and absorption efficiency via evanescent coupling. These ultra-thin superconducting MoSi detectors are precisely patterned on top of a single mode Si waveguide (600 nm) with alignment error less than 40 nm. Low temperature electrical and nano-optical characterization was carried out using a two-stage pulse tube (PT) coldhead, using an additional 4He / 3He sorption pump, low vibration characterization of SNSPD devices at 350 mK was carried out. Characterised devices exhibit low dark count rate <5 counts per second and timing jitter of ≈ 83 ps full width half maximum (FWHM) at wavelength (λ) = 1550 nm and at critical current ≈ 30 µA.