Superconducting nanowire single-photon detectors(SSPDs or SNSPDs) can detect single photons in a wide spectrum range from ultraviolet to mid-infrared wavelengths. We developed SSPDs for the light wavelength of 900-1100 nm, where it is difficult to achieve high detection efficiency by either Si or InGaAs avalanche photodiodes. We designed and fabricated the SSPD with non-periodic dielectric multilayers (DMLs) composed of SiO2 and TiO2 to enhance the optical absorptance in the wavelength range of 900-1100 nm. We measured the detection efficiency (DE) in the wavelength range of 800-1360 nm using a supercontinuum light source and found that the wavelength dependence of DE was in good agreement with the simulated spectrum of the optical absorptance of the nanowire device on the designed DML. The highest system DE was 81.0% for the wavelength of 980 nm.
Superconducting nanowire single-photon detectors(SSPDs or SNSPDs) can detect single photons in a wide spectrum range from ultraviolet to mid-infrared wavelengths. We developed SSPDs for the light wavelength of 900-1100 nm, where it is difficult to achieve high detection efficiency by either Si or InGaAs avalanche photodiodes. We designed and fabricated the SSPD with non-periodic dielectric multilayers (DMLs) composed of SiO2 and TiO2 to enhance the optical absorptance in the wavelength range of 900-1100 nm. We measured the detection efficiency (DE) in the wavelength range of 800-1360 nm using a supercontinuum light source and found that the wavelength dependence of DE was in good agreement with the simulated spectrum of the optical absorptance of the nanowire device on the designed DML. The highest system DE was 81.0% for the wavelength of 980 nm.
Abstract The detection efficiency (DE) of superconducting nanowire single-photon detectors (SNSPDs) at 1550 nm has been significantly improved in the past decades as a result of evolution of the optical structure, the materials, and the fabrication process. We discuss the general optical design for a high-efficiency SNSPD based on dielectric optical films that can detect wavelengths from visible to near infrared regions. This structure shows close-to-unity absorption and good insensitivity to the fine wavelength and the incident angle. We demonstrate an SNSPD specifically fabricated for the detection of 1064 nm wavelength with a maximal system DE of 87.4% ± 3.7%. The DEs of the SNSPDs for visible and near infrared wavelengths are also summarized and compared with those of semiconducting detectors.
We present superconducting nanowire single-photon detectors (SSPDs) on non-periodic dielectric multilayers, which enable us to design a variety of wavelength dependences of optical absorptance by optimizing the dielectric multilayer. By adopting a robust simulation to optimize the dielectric multilayer, we designed three types of SSPDs with target wavelengths of 500 nm, 800 nm, and telecom range respectively. We fabricated SSPDs based on the optimized designs for 500 and 800 nm, and evaluated the system detection efficiency at various wavelengths. The results obtained confirm that the designed SSPDs with non-periodic dielectric multilayers worked well. This versatile device structure can be effective for multidisciplinary applications in fields such as the life sciences and remote sensing that require high efficiency over a precise spectral range and strong signal rejection at other wavelengths.
High-efficiency superconducting nanowire single-photon detectors (SNSPDs), which have numerous applications in quantum information systems, function by using the optical cavity and the ultrasensitive photon response of their ultra-thin superconducting nanowires. However, the wideband response of superconducting nanowires is limited due to the resonance of the traditional optical cavity. Here, we report on a supercontinuum SNSPD that can efficiently detect single photons over an ultra-broad spectral range from visible to mid-infrared light. Our detection approach relies on using multiple cavities with well-separated absorbed resonances formed by fabricating multilayer superconducting nanowires on metallic mirrors with silica acting as spacer layers. Thus, we are able to extend the absorption spectral bandwidth while maintaining considerable efficiency, as opposed to a conventional single-layer SNSPD. Our calculations show that the proposed supercontinuum SNSPD exhibits an extended absorption bandwidth with increased nanowire layers. Its absorption efficiency is greater than 70% over the entire range from 400 to 2500 nm (or 400 to 3000 nm), when using two-layer (or three-layer) nanowires. As a proof of principle, the SNSPD with bilayer nanowires is fabricated based on the proposed detector architecture with simplified geometrical parameters. The detector achieves broadband detection efficiency over 60% from 950 to 1650 nm. This type of detector may replace multiple narrow band detectors in a system and find uses in the emerging and rapidly advancing field of atomic and molecular broadband spectroscopy.
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.
Implementations of quantum information require single-photon detectors (SPDs) with high detection efficiency (DE) at a wavelength of 940 nm, which is a challenge for the available semiconducting SPDs. Superconducting nanowire SPDs (SNSPDs) are capable of detecting visible and near-infrared single photons with high DE. However, these detection capabilities place stringent design requirements on the cavity and nanowire geometry structures. We design, fabricate, and measure SNSPDs with high DE optimized for the 940-nm wavelength. The NbN SNSPDs were fabricated on 1-D photonic crystals for high optical absorptance. By tuning the filling factor of the nanowire through numerical simulations and experiments, we were able to obtain an SNSPD (7 nm thick, 125 nm width, and 0.57 filling factor, as well as active area of18∗18μm) with a saturated system DE of 83.6$\pm3.7\pm$0.02. To our best knowledge, this is the highest value reported for NbN SNSPDs at 940-nm wavelength. The availability of an SNSPD with high system DE at 940 nm may have a profound impact in the field of photonic quantum technologies, such as multiphoton entanglement.
Nanowire superconducting single-photon detectors (SSPDs) consist of a superconducting wire of nanoscale cross-section [1], typically 4×100 nm2. A current close to the device critical current renders the nanowire sensitive to single photons. SSPDs are known for their high efficiency, low jitter, low dark count rate and fast reset time. An important challenge for future application of SSPDs is to extend the useful wavelength range towards the infrared without comprising detector speed or dark count rate. To this end, we explore optical designs with wider nanowires that utilize efficient detection of single photons at the edge of the nanowire. Silicon nanowires on top of a NbN nanowire increase both the calculated total absorption and the internal detection efficiency significantly compared to a standard meandering wire geometry.