Transmission properties of a high critical temperature superconductor-dielectric multilayer photonic band gap structure

In the last decade, substantial effort has been made to analyze the transmission properties of so-called “Photonic Band Gap” structures in one, two, and three dimensions. These structures take advantage of combinations of materials with differing indices of refraction in multilayer periodic (or quasi-periodic) fashion to obtain an optical structure with interesting transmission properties. A wide variety of PBG structures have been described in literature, including dielectric/dielectric, semiconductor/dielectric, and metal/dielectric multilayered combinations.; Superconducting materials have been known to exist at very low temperatures since Kamerlingh Onnes made his discovery in 1911. Since about 1987 superconductivity has been demonstrated above liquid nitrogen temperatures (so-called “high temperature” superconductors), making applications of superconductors more practical. Research has demonstrated that superconductivity can be “quenched” with an incident electromagnetic field above some “critical” intensity, and the superconductivity is restored when the radiation intensity is reduced below the critical value. It is also known that superconductors undergo a change in optical properties as the transition is made between the superconducting (S) and normal (N) state.; This work uses Time-Dependent Ginzburg-Landau theory to model the change in the dielectric function as YBCO undergoes the S/N transition, then calculates the transmittance properties in the frequency range from 5000nm (near infrared) to 200nm (near ultraviolet) of a one-dimensional multi-layer PBG structure made up of alternating layers of a high-temperature superconductor (HTS), namely YBCO, and a dielectric. The structure obtained by layering these two materials multiple times exhibits transmittance characteristics greatly enhanced over that expected for a single slab of solid YBCO with an equal bulk thickness. The transmission spectrum exhibits bands of high transmittance and almost total reflectance, and depends on whether the YBCO is superconducting or not, therefore suggesting the possibility of a very fast (sub-picosecond) fully optical switch. The frequency dependent critical beam intensity is calculated.; Previous research has demonstrated generation of second and third harmonic optical signals in superconductors under appropriate conditions. It is demonstrated here that a high-temperature superconductor/dielectric PBG structure should be useful for generating both harmonics in a very compact (only several microns thick), relatively easily fabricated device.