Self-aligned multi-channel superconducting nanowire single-photon detectors

Abstract

We describe a micromachining process to allow the coupling of an array of single-mode telecommunication fibers to individual superconducting nanowire single photon detectors (SNSPDs). As proof of principle, we show the integration of four detectors on the same silicon chip, including two standard single-section nanowire detectors and two superconducting nanowire avalanche photodetectors (SNAPs) with modified series structure without external inductor, and their performances are compared. The SNAP shows saturated system detection efficiency of 16% while the dark count rate is less than 20 Hz, without the use of photon-recycling reflectors. The SNAP also demonstrates doubled signal-to-noise ratio, reduced reset time (~ 4.9 ns decay time) and improved timing jitter (62 ps FWHM) compared to standard SNSPDs.In recent years, superconducting nanowire single-photon detectors (SNSPDs) 1,2 have emerged as successful alternatives to traditional InGaAs/InP-based single-photon avalanche photodiodes (SPADs) in the realm of near-infrared single photon detection due to their excellent quantum efficiency, 3-6 short timing jitter, 6-8 ultralow dark count rates, 9-11 fast reset time with only several nanoseconds, 6,12,13 and photon number resolving ability. [14][15][16] To date, most of SNSPD systems utilize fiber coupling method because of advantages over free-space coupling, including lower dark count rates, more compact size and robustness to vibration. However, precise alignment between the beam-spot (~10 m in diameter) from single-mode fiber and active nanowire area (typically 10-15 m in diameter) still remains challenging, in particular for robust, multi-cycle operation at low temperatures. Three dimensional cryogenic positioner in combination with fiber focuser is commonly employed for in situ matching of the beam waist to the detection area of the nanowire detector. 17 High-efficiency fiber-to-detector coupling can be realized in this way but only one detector can be addressed at a time. Recently, a self-aligned coupling method based on deep-etching of silicon wafer was proposed by the NIST group. 18Using this technique, a front-illuminated WSi-based SNSPD was realized and achieved an impressive 93% system efficiency, boosted by a reflector and cavity embedded between the superconducting nanowire and the substrate. 4 Here, we demonstrate a backside silicon micromachining process that allows the precision placement of cleaved fiber in the etched pit in a self-aligned fashion while NbTiN superconducting nanowires are fabricated on the front side.

Superconducting Nanowires for Single‐Photon Detection: Progress, Challenges, and Opportunities

“…From a practical measurable device characteristic point of view, reset time is measured as the time at which the voltage between the two electrodes decays (Figure ). Typically, this curve of voltage versus time can be simplify fit to an exponent for obtaining the device reset time . Kerman et al .…”

Broadband on-chip single-photon spectrometer

“…3d. For some of the devices, two nanowires are connected in parallel to boost the signal-to-noise ratio (SNR) [36][37][38] while still maintaining the saturated internal detection efficiency (see In order to minimize the extra timing jitter induced by the electronic noises from the readout circuits and thus maximize the spectral resolution, we employ two SiGe cryogenic low-noise amplifiers (Cosmic Microwave Technology CITLF1) operating at 4 K temperature to read out the photon-excited detector pulses (see Supplementary Note 5).…”

Photon-Photon Quantum Phase Gate in a Photonic Molecule with χ(2) Nonlinearity

“…For adiabatic retrieval process, the input and driving fields are smooth. It is reasonable to adiabatically eliminate c 10 .…”