Optical control of magnetic flux quanta in YBCO thin film loops by selected femtosecond laser pulses

We report on an optical magnetic flux control in high-Tc superconductive loops and films using a femtosecond (fs) laser. The YBa ₂Cu₃O_7-δ (YBCO) films are patterned into strips with two rectangular parallel holes, with ordered arrays of antidots, or without any holes. The fs optical pulses are focused onto the strips while biasing the current. After removal of the bias current, the supercurrent density distributions are visualized by terahertz radiation imaging. The images indicate that the flux and anti-flux quanta are optically generated in the strips, and the number of the flux quanta between 15 and 2000 flux quantum is controlled by both the bias current and laser power. We then put forward the system to control the number of the fs pulses to generate the flux. The results reveal that even single shot fs optical pulse can generate the flux quanta in the strips