Ultrathin optical switch based on a liquid crystal/silver nanoparticles mixture as a tunable indefinite medium

摘要

We predict that a liquid crystal/silver nanoparticles mixture can be designedso that, in a frequency range, its effective ordinary and extraordinarypermittivities have real parts of different signs. We exploit this result todesign a nano-photonic device obtained by sandwiching a few hundred nanometerthick slab of the proposed mixture between two silica layers. By resorting tofull-wave simulations, we show that, by varying the direction of an externallyapplied electric field, the device can be used as an optical modulator sinceits transmissivity can be switched between 0.02 and 0.4 at a wavelength closeto the frequency range where the medium is indefinite. The device functionalityphysically stems from the fact the orientation of the hyperbola characterizingextraordinary waves within the indefinite medium follows the applied electricfield direction and therefore, if the hyperbola asymptote is nearly normal tothe slab, full switch between evanescent and homogeneous propagating waves canbe achieved within the medium.