Laser-induced optical index gratings on superconducting thin film structures

A theory is presented that demonstrates that a superconducting thin film under laser illumination can form an optical index grating similar to those created in nonlinear dielectric media. The grating consists of a spatially varying quasiparticle density in accordance with the intensity of a laser interference pattern. The analysis shows that such laser-induced optical index gratings form rapidly, on the order of 0.5 nsec, and can be detected via the diffraction of millimeter waves.