Enhanced telecom wavelength single-photon detection with NbTiN superconducting nanowires on oxidized silicon
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(a) Full chip and fiber arrangement, not to scale. (b) Simulated probability of photon absorption in NbTiN layer . (c) Simulated electric field in device layers assuming photons incident in a device area with . (d) Experimental arrangement for DE measurements. Current is supplied below through the dc line of the bias , while pulses are read out through the ac line. Laser diodes of different wavelengths are attenuated to provide a controlled photon flux (via calibrated in-fiber attenuation). A manual polarization controller is used to match the optimum photon polarization to the device orientation.
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(a) Device detection efficiency vs dark count rate at three wavelengths. Polarization optimized for high (low) efficiency shown as squares (circles). Note: vertical scales vary. (b) Polarization-dependent measurement of DE over a wide wavelength range with 700 Hz dark count rate. (Main plot) Detection efficiency with fixed input polarization set to maximize (minimize) response at 1550 nm shown as solid (dashed) line. (Inset) Average of the two results from the main plot shown as dashed line. Data taken with the polarization scrambling method shown as solid line precisely aligning with the averaged data. (c) DE with varying wavelength at 1.7 kHz dark count rate. (Main plot) Average of measurements taken with polarization set for high and low response at reference wavelengths to produce a polarization independent result. Vertical dashed line marks the designed absorption maximum. (Inset) Simulated data with .
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