Optically induced quasiparticle density profiles in superconducting thin films.

Abstract

We present numerical solutions of the coupled phonon-quasiparticle rate equations, with quasiparticle (qp) and phonon diffusion included, for a superconducting thin film illuminated by a temporally pulsed and spatially inhomogeneous optical intensity pattern. We consider optical intensities in the form of both a finite circular spot with a Gaussian cross section and a sinusoidal interference pattern. Thereby we demonstrate that spatially well-defined qp density profiles, including a qp grating, can be optically induced on nanosecond time scales. For the qp grating we use the ${\mathit{T}}^{\mathrm{*}}$ formalism to calculate the resulting conductivity grating in the film, and then calculate the grating diffraction peaks for incident microwaves.