Vector mapping of supercurrent flow in YBCO thin films using polarization of THz radiation excited by femtosecond laser pulses

Abstract

THz radiation is emitted into free space from YBCO thin films by exciting with femtosecond laser pulses under a bias current, magnetic field, and magnetic-flux trapped state. The emission mechanism is proposed to originate from the ultrafast supercurrent modulation by optical pulses. The amplitude of the radiation is proportional to the supercurrent density at the exciting laser spot and it is polarized along the current direction. Formerly, we proposed and demonstrated that the two-dimensional supercurrent distribution can be visualized by scanning the laser spot with detecting the radiation amplitude. We propose a new system for vector mapping of the supercurrent flow by detecting the amplitude and polarization direction of the THz radiation.