Studying the position dependent absorption efficiency of superconducting single photon detectors (SSPD) is essential for understanding its detection process. We set out to assemble a scattering...Show moreStudying the position dependent absorption efficiency of superconducting single photon detectors (SSPD) is essential for understanding its detection process. We set out to assemble a scattering-scanning near field optical microscope (s-SNOM) capable of probing photons at sub 30 nm resolution. Tuning forks with glued tip are used in the aim of building a low temperature AFM. Temperature and pressure dependence of the tuning fork’s resonance frequency and quality factor have been studied. Temperature fluctuations during AFM scanning have been shown to cause height deviations of up to 650 mm/K at atmospheric pressure depending on the tip. AFM scanning has been successful at imaging a calibration sample with a height difference of 200 nm and locating 50 nm high meandering nanowire features of a MoGe SSPD.Show less
We investigate photon counting properties in an NbN superconducting nanodetector, and succesfully do quantum detector tomography. We find qualitative similarities to an earlier tomography result on...Show moreWe investigate photon counting properties in an NbN superconducting nanodetector, and succesfully do quantum detector tomography. We find qualitative similarities to an earlier tomography result on the same detector, although a larger power range may eliminate anomalies in the numerical fit. Furthermore, we investigate the resistive properties of a MoSi superconducting nanodetector, observing finite resistance below the critical temperature. Measuring current as a function of voltage, we find indications that indeed imply a finite resistance below Tc. Obtaining the critical current for different temperatures and applying a Ginzburg-Landau fit, we find a lower critical temperature than obtained from measurements of resistance as a function of temperature. Finally, we observe that photon counts for MoSi are not possible above T > 3.85 K. We calculate that electronic noise is responsible for this absence of photon counts.Show less
