Elasto-optical effect on the band structure of a one-dimensional photonic crystal under hydrostatic pressure

The devices formed using photonic crystals are based on the response to physical stimuli and depend on the properties of the media. Recently, there has been an increase in the application of photonic crystals in several fields through the use of several techniques. In particular, multilayer films are used as filters and reflectors in the THz range and as pressure sensors. The band structure of a 1D photonic crystal under hydrostatic pressure was studied. The materials used for the alternating layer structures were considered homogeneous, isotropic, elastic, and non-magnetic. The change in permittivity of the materials was calculated using the elasto-optical effect. The frequency spectrum of the photonic crystal was determined from the eigenvalues equation for the magnetic intensity vector using the plane wave expansion method. Two photonic arrangements with different mechanical properties were proposed: poly(methyl methacrylate)-polystyrene, and poly(methyl methacrylate)-silica. Numerical results showed that the bandgap of both arrangements tend toward higher frequencies when the hydrostatic pressure increases and that the bandgap width varies with the hydrostatic pressure. It was concluded that, if the mechanical properties of both layers are similar, such as in the case of polymers, the bandgap width is constant. If the layer with the higher permittivity is less rigid than the other layer, such as in the second arrangement, the bandgap width reaches a minimum at a determined value of the pressure.