Abstract

Niobium is an important superconducting metal for the fabrication of Josephson junctions and other superconducting devices. One of the parameters which governs the ultimate switching speed of a Josephson junction is the electron-phonon relaxation time. Using ultrafast laser excitation on the Josephson junction¹,², the transition from superconducting to normal and back to superconducting state is monitored by the transient change in voltage across the junction¹,². The rise time of the transient change of voltage is mainly governed by the electron-phonon relaxation time which is ultrafast and cannot be resolved by voltage measurement. In this talk, the electron-phonon relaxation time and electron-phonon coupling constant of niobium was measured by a time resolved thermal modulation³-⁵ optical transmission technique.

© 1990 Optical Society of America