Abstract
We evaluate the performance of a mid-infrared emission spectrometer operating at wavelengths between 1.5 and 6 μm based on an amorphous tungsten silicide (a-WSi) superconducting nanowire single-photon detector (SNSPD). We performed laser induced fluorescence spectroscopy of surface adsorbates with sub-monolayer sensitivity and sub-nanosecond temporal resolution. We discuss possible future improvements of the SNSPD-based infrared emission spectrometer and its potential applications in molecular science.
Highlights
Technologies for infrared single-photon detectors have emerged during the last few decades
3.1 Detection efficiency of the fiber-superconducting nanowire single-photon detector (SNSPD) assembly in mid-IR Figure 2 presents measured absolute detection efficiencies (DE) of the fiber-SNSPD assembly used in this work
For each wavelength the photon counting rate (PCR) of the SNSPD is recorded as Ib is scanned from zero to the current at which the nanowire switches from the superconducting to the normal state (Isw = 6.5 μA)
Summary
Technologies for infrared single-photon detectors have emerged during the last few decades. SNSPDs operate at low temperatures (typically 4K or below), miniaturized and low-maintenance cryogen-free systems are developed and commercially available [15,16,17], making them a key enabling technology for various near-infrared applications, including fundamental test of quantum optics [18], quantum key distribution [19], space-to-ground optical communication [20], light detection and ranging (LIDAR) [21], and singlet oxygen luminescence detection [22] Extension of such performance into the mid-IR opens a path to a wide range of applications where extremely high sensitivity and excellent temporal resolution is required for molecular spectroscopy. One approach employed fabrication of ultra-narrow (< 50 nm) nanowires with superconducting materials such as NbN [23, 24]; the requirement of narrow widths significantly reduces the yield for large-area detectors due to fabrication imperfections Another approach exploits new superconducting nanowire materials - e.g. amorphous tungsten silicide (a-WSi) alloy. SNSPD devices based on WSi developed by Nam et al have demonstrated saturated internal quantum efficiency from 2.1 to 5.5 μm wavelength [25]
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