Local surface plasmon tuning for optical devices

Confining light to nanoscale dimensions has become possible with surface plasmons. However, active control of plasmonic responses remains a hurdle for building plasmonic optical devices. In this letter, we analytically derive a model describing the gap between the local surface plasmon (LSP) modes of a spherical nanoparticle in anisotropic media as a function of applied external electric field. Anisotropic ferroelectric materials exhibit birefringence that can be controlled through the electro-optic effect. Hence, the splitting of LSP frequencies in ferroelectrics embedded with nanoparticles can be controlled. In other words, by applying an external voltage a transition between the anisotropic and the isotropic phases can be achieved. As a result, the gap created by anisotropy can be tuned by the applied voltage. We derive and provide an explanation to the required field intensity according to the coercive field of ferroelectric materials. This simple approach is the basis for a method to actively tune the amplitude and the polarizability of light. The method can be considered for photonic applications, such as optical switches and biomedical sensors.