Leiden University Student Repository

Saez-Mollejo, Saez (2017)

Multi-photon polarization dependence of SSPDS

Bachelor thesis | Natuurkunde (BSc)

We study superconductivity and photon detection in a NbN nanobridge of 150 nm width and 4 nm thickness. Superconductivity is observed below Tc = 8.4K. The measured critical current as a function of temperature shows a slow decrease up to 7.9 K and more rapid decrease between 7.9 K and 8.4K. Light counts are only observed below T = 8.4K and dark counts below 7.85K. We characterize the detector by measuring the count rate as a function of polarization and average power to explore a multi-photon polarization dependence. We find a large difference in the response curves of the detector that cannot be explained by a change in the absorption efficiency h. Unfortunately, at the moment of writing the origin of the effect is inconclusive and is at least partly caused by a shift in the position of the focused laser beam on the sample when rotating a l/2 plate to change the polarization

superconductors

single photon detection

tomography

Author

Saez-Mollejo, Saez

Faculty

Faculty of Science

Supervisors

Dood, Michiel de

ECTS Credits

3

Language

en