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Xiaolong Hu, Holzwarth, C. W., Masciarelli, D., Dauler, E. A., & Berggren, K. K. (2009). Efficiently coupling light to superconducting nanowire single-photon detectors. IEEE Trans. Appl. Supercond., 19(3), 336–340.
Abstract: We designed superconducting nanowire single-photon detectors (SNSPDs) integrated with silver optical antennae for free-space coupling and a dielectric waveguide for fiber coupling. According to our finite-element simulation, (1) for the free-space coupling, the absorptance of the NbN nanowire for TM-polarized photons at the wavelength of 1550 nm can be as high as 96% by adding silver optical antennae; (2) for the fiber coupling, the absorptance of the NbN nanowire for TE-like-polarized photons can reach 76% including coupling efficiency at the wavelength of 1550 nm by adding a silicon nitride waveguide and an inverse-taper coupler.
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Feautrier, P., le Coarer, E., Espiau de Lamaestre, R., Cavalier, P., Maingault, L., Villégier, J. - C., et al. (2008). High-speed superconducting single photon detectors for innovative astronomical applications. In J. Phys.: Conf. Ser. (Vol. 97, 10).
Abstract: Superconducting Single Photon Detectors (SSPD) are now mature enough to provide extremely interesting detector performances in term of sensitivity, speed, and geometry in the visible and near infrared wavelengths. Taking advantage of recent results obtained in the Sinphonia project, the goal of our research is to demonstrate the feasibility of a new family of micro-spectrometers, called SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer), associated to an array of SSPD, the whole assembly being integrated on a monolithic sapphire substrate coupling the detectors array to a waveguide injecting the light. This unique association will create a major breakthrough in the domain of visible and infrared spectroscopy for all applications where the space and weight of the instrument is limited. SWIFTS is an innovative way to achieve very compact spectro-detectors using nano-detectors coupled to evanescent field of dielectric integrated optics. The system is sensitive to the interferogram inside the dielectric waveguide along the propagation path. Astronomical instruments will be the first application of such SSPD spectrometers. In this paper, we describes in details the fabrication process of our SSPD built at CEA/DRFMC using ultra-thin NbN epitaxial films deposited on different orientations of Sapphire substrates having state of the art superconducting characteristics. Electron beam lithography is routinely used for patterning the devices having line widths below 200 nm and down to 70 nm. An experimental set-up has been built and used to test these SSPD devices and evaluate their photon counting performances. Photon counting performances of our devices have been demonstrated with extremely low dark counts giving excellent signal to noise ratios. The extreme compactness of this concept is interesting for space spectroscopic applications. Some new astronomical applications of such concept are proposed in this paper.
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Annunziata, A. J., Quaranta, O., Santavicca, D. F., Casaburi, A., Frunzio, L., Ejrnaes, M., et al. (2010). Reset dynamics and latching in niobium superconducting nanowire single-photon detectors. J. Appl. Phys., 108(8), 7.
Abstract: We study the reset dynamics of niobium (Nb) superconducting nanowire single-photon detectors (SNSPDs) using experimental measurements and numerical simulations. The numerical simulations of the detection dynamics agree well with experimental measurements, using independently determined parameters in the simulations. We find that if the photon-induced hotspot cools too slowly, the device will latch into a dc resistive state. To avoid latching, the time for the hotspot to cool must be short compared to the inductive time constant that governs the resetting of the current in the device after hotspot formation. From simulations of the energy relaxation process, we find that the hotspot cooling time is determined primarily by the temperature-dependent electron-phonon inelastic time. Latching prevents reset and precludes subsequent photon detection. Fast resetting to the superconducting state is, therefore, essential, and we demonstrate experimentally how this is achieved. We compare our results to studies of reset and latching in niobium nitride SNSPDs.
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Baek, B., Lita, A. E., Verma, V., & Nam, S. W. (2011). Superconducting a-WxSi1–x nanowire single-photon detector with saturated internal quantum efficiency from visible to 1850 nm. Appl. Phys. Lett., 98(25), 3.
Abstract: We have developed a single-photon detector based on superconducting amorphous tungsten–silicon alloy (a-WxSi1–x) nanowire. Our device made from a uniform a-WxSi1–x nanowire covers a practical detection area (16 μm×16 μm) and shows high sensitivity featuring a plateau of the internal quantum efficiencies, i.e., efficiencies of generating an electrical pulse per absorbed photon, over a broad wavelength and bias range. This material system for superconducting nanowire detector technology could overcome the limitations of the prevalent nanowire devices based on NbN and lead to more practical, ideal single-photon detectors having high efficiency, low noise, and high count rates.
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Mohan, N., Minaeva, O., Goltsman, G. N., Saleh, M. F., Nasr, M. B., Sergienko, A. V., et al. (2009). Ultrabroadband coherence-domain imaging using parametric downconversion and superconducting single-photon detectors at 1064 nm. Appl. Opt., 48(20), 4009–4017.
Abstract: Coherence-domain imaging systems can be operated in a single-photon-counting mode, offering low detector noise; this in turn leads to increased sensitivity for weak light sources and weakly reflecting samples. We have demonstrated that excellent axial resolution can be obtained in a photon-counting coherence-domain imaging (CDI) system that uses light generated via spontaneous parametric downconversion (SPDC) in a chirped periodically poled stoichiometric lithium tantalate (chirped-PPSLT) structure, in conjunction with a niobium nitride superconducting single-photon detector (SSPD). The bandwidth of the light generated via SPDC, as well as the bandwidth over which the SSPD is sensitive, can extend over a wavelength region that stretches from 700 to 1500 nm. This ultrabroad wavelength band offers a near-ideal combination of deep penetration and ultrahigh axial resolution for the imaging of biological tissue. The generation of SPDC light of adjustable bandwidth in the vicinity of 1064 nm, via the use of chirped-PPSLT structures, had not been previously achieved. To demonstrate the usefulness of this technique, we construct images for a hierarchy of samples of increasing complexity: a mirror, a nitrocellulose membrane, and a biological sample comprising onion-skin cells.
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