Submicrometer photoresponse mapping of nanowire superconducting single-photon detectors
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Photoresponse mapping setup. This configuration affords high resolution scanning over a area without SIL and with SIL. The confocal microscope has a short working distance and high NA. The sample is mounted on a low temperature piezoelectric translation stage. The device is electrically connected for biasing and readout of photodetection events. SSPD, nanowire superconducting single photon detector; SIL, hemispherical solid immersion lens; SMF, single mode optical fiber; cw laser, continuous wave laser. Inset: a scanning electron micrograph (SEM) of a nanowire SSPD as used in this study ( linewidth, period, and area).
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(Color online) Photoresponse signatures of nanowire SSPDs (using setup depicted in Fig. 1). Sample temperature of . (a) Higher detection efficiency (DE) area device. No SIL, , , and scanning area . Inset (i): upper trace, profile of high resolution scan over edge with fit. In the lower trace, the FWHM from the differentiated fit is . Inset (ii): inductance versus bias current at . The inductance at zero bias is and increases by 8% toward the critical current . (b) Lower DE area device. SIL , , , and high resolution scan of area. Inset (i): profiles in orthogonal scanning directions. FWHM from Gaussian fits: 313 and , respectively. Inset (ii): inductance versus bias current at . The inductance at zero bias is and increases by 3% toward the critical current .
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