Detection and Measurement of Picoseconds-Pulsed Laser Energy Using a NbTiN Superconducting Filament

• Published in: IEEE transactions on applied superconductivity Vol. 33; no. 5; pp. 1 - 5
• Main Authors: Harrabi, K., Gasmi, K., Mekki, A., Bahlouli, H., Kunwar, S., Milosevic, M. V.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Critical current (superconductivity); Critical current density; Delay time; Delays; hotspot; Laser beams; Lasers; Light sources; Measurement by laser beam; non-equilibrium superconductivity; Optical pulses; Optical vortices; Photonics; Pulsed lasers; superconducting single photon detection; Superconductivity; Time dependence; Voltage measurement
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2023.3243193

We investigate non-equilibrium states created by a laser beam incident on a superconducting NbTiN filament subject to an electrical pulse at 4 K. In absence of the laser excitation, when the amplitude of the current pulse applied to the filament exceeds the critical current value, we monitored the delay time <inline-formula><tex-math notation="LaTeX">t_{d}</tex-math></inline-formula> that marks the collapse of the superconducting phase which is then followed by a voltage rise. We linked the delay time to the applied current using the time-dependent Ginzburg-Landau (TDGL) theory, which enabled us to deduce the cooling (or heat-removal ) time from the fit to the experimental data. Subsequently, we exposed the filament biased with a current pulse close to its critical value to a focused laser beam, inducing a normal state in the impact region of the laser beam. We showed that the energy of the incident beam and the incurred delay time are related to each other by a simple expression, that enables direct measurement of incident beam energy by temporal monitoring of the transport response. This method can be extended for usage in single-photon detection regime, and be used for accurate calibration of an arbitrary light source.