Temperature dependence of the inelastic reflection of light off a superconductor

We give a general formulation for the problem of scattering of light off the surface of a superconductor with the creation of two quasiparticles. The cross-section is evaluated at all temperatures for a pure superconductor; at zero temperature the result agrees with earlier calculations by Abrikosov and Falkovskii and by Tong and Maradudin. At zero temperature there is no scattering with a frequency shift ω of less than 2Δ; as the temperature increases the scattering for ω<2 Δ increases progressively because of the increasing number of thermally excited quasiparticles.