Control of the light extraction from a photonic crystal nanocavity by coupling with a nanoparticle

Abstract

Abstract In this paper, we present a numerical study (using Finite Difference Times Domain (FDTD) method) of the coupling between two resonant structures with different quality factors of their resonances. The first is a Photonic Crystal Cavity (PCC) while the second is a dielectric Nano-Particle (NP). Both structures exhibit optical responses at the same wavelength, which allows a critical coupling between them. The objective of the study is to exploit this coupling to control the light extraction properties of the more resonant structure (the PCC). The challenge is then: first, to model such a near-field coupling through numerical method that can handle the entire structure (PCC+NA) and second, to get physical insight about the interaction allowing a good control of the light extraction. We numerically demonstrate that this coupling strongly depends on the spatial position of the NP relative to the PCC. We also show that the direction of the emission (into the substrate or superstrate) and its intensity can be adjusted by the NP position relative to the PCC. Quantitatively, the critical coupling corresponds to an NP-PCC distance of 120 nm leading to an increase by factor of 3 of the light radiated towards the far field. This is accompanied by a red shift of 0.53 nm of the cavity resonance. This study opens the way to the development of a new kind of sources with both ‘controllable’ wavelength resonance and radiation pattern.