Electrically tunable ferroelectric liquid-crystal Fabry-Perot filter.

An electrically operated device that can switch between two wavelengths is described. The device operates by using an electrically switchable optically anisotropic material such as a liquid crystal in a Fabry-Perot cavity. The anisotropy produces two distinct cavity resonances that determine the two wavelengths. The electric field interchanges the slow and the fast optical axes of the anisotropic ferroelectric liquid crystal and thus allows switching from one wavelength to the other. It is shown that this device structure can be used as a polarization-sensitive switch with an extinction ratio of better than 100:1. This is true only for a class of ferroelectric liquid-crystal material that has a title angle of 45 degrees .