Terahertz radiation imaging of vortex penetration into YBCO thin films with and without ordered arrays of antidots

Terahertz radiation imaging has been employed to diagnose the supercurrent and vortex distribution in high-T-c superconductive thin film strips. We ob serve them in the YBCO films patterned into the strip with and without orde red arrays of small antidots. Comparison with theoretically expected distri bution reveals that the present technique can provide a powerful tool for t he noncontact, nondestructive, and free-space evaluation of the supercurren t and the vortex distribution with good quantitative agreement. The effect of the antidot formation in the strips is explained by the decrease of the effective critical current. The remanent state after removal of the relativ ely large magnetic field cannot be explained by the conventional model for the superconductive thin films and the discrepancy is more notable in the a ntidot formed area.