Mechanically controlled bandgap in cholesteric elastomers

The propagation of an electromagnetic wave traveling in a chiral elastomer under the influence of an externally induced mechanical strain, applied parallel to the helical axis, is investigated. We write and solve Maxwell equations in the Oseen reference system by performing a numerical integration to find the transmission and reflection coefficients as a function of the mechanical elongation and the incidence angles. Then, the transmittances and the reflectances are calculated and analyzed. A mechanically controlled circular Bragg phenomenon is observed for which the bandwidth and the central wavelength are significantly modified. It is also shown that the reflection bandgap blue-shifts versus the incidence angles, as happens in absence of strain.