Design analysis of hybrid silicon-on-nothing photonic crystal-nanoantenna structures for engineering of midinfrared radiative properties

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Electromagnetic (EM) behaviors of photonic crystals (PhCs) and nanoantenna (NA) arrays have been extensively studied and applied to a myriad of applications, including light absorption, surface-enhanced Raman scattering, light trapping in photovoltaics, and spectral narrowing of thermal emission. However, not many works have studied the integration of three-dimensional (3-D) PhCs and NA arrays into one structure mainly due to technical challenges in manufacturing 3-D PhCs. The present article reports the design analysis of a hybrid optical structure that has a gold rectangular NA array aligned on a 3-D silicon-on-nothing (SON) PhC substrate. By applying a continuous phase field model, we numerically simulate the formation of SON-PhC structures (i.e., a 3-D periodic array of spherical voids in silicon) during the high-Temperature annealing process of a silicon substrate having vertical trenches. Photonic behaviors of the NA-on-SON PhC structure are computed using the finite-difference time-domain method. The obtained results exhibit the resonant absorption of midinfrared (mid-IR) light in the stopping bands of the SON-PhC (3.0μm<λ<7.5μm) by photon coupling with the free electron oscillations in each NA structure. This PhC-mediated NA resonance is manifested by highly concentrated electric fields at NA corners; the corresponding local field enhancement factor is one order of magnitude greater than that of the NA array on a bare silicon substrate.

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Journal of Nanophotonics