Electro-optical modulator using tunable III-V semiconductor in nanocavity

Fabry-Perot nanocavities are widely used in nanophotonic applications due to their exceptional electromagnetic properties and subwavelength dimensions. The spectral response of these nanocavities is primarily governed by the separation between the reflecting mirrors and the refractive index of the spacer material. In this study, we present dynamic control over the resonance wavelength of a Fabry-P´erot nanocavity by incorporating an n-type doped indium antimony (n-InSb) layer as a tunable semiconductor within the nanocavity spacer. To achieve dynamic tuning, we exploit the sizable nonlinear response of the plasma frequency of the n-InSb as a function of electron concentration. The accumulation of electrons by applied voltage within a sublayer of n-InSb in a metal-oxide-semiconductor-oxide-metal nano structure enables a variation in total phase delay of the Fabry-Perot nanocavity. This facilitates a maximum effective optical modulation of about 91% at reasonably low applied voltage. The study predicts a 95 nm blue shift in a visible frequency Fabry-Perot resonance. The study also provides details on the carrier dynamics of n-InSb at applied voltage on one or both metal surfaces.