Design of an Optical Trapping Device Based on an Ultra-High Q/V Resonant Structure

A novel photonic/plasmonic cavity based on a 1-D photonic crystal cavity vertically coupled to a plasmonic gold structure is reported. The design has been optimized to achieve an ultra-high Q/V ratio, therefore improving the light-matter interaction and making the device suitable for optical trapping applications. Accurate 3-D finite element method (FEM) simulations have been carried out to evaluate the device behavior and performance. The device shows Q = 2:8 × 10³ and V = 4 × 10^-4(λ=n)³, which correspond to a Q=V = 7 × 10⁶(λ=n)^-3 with a resonance transmission around 50% at λ_R = 1589:62 nm. A strong gradient of the optical energy has been observed in the metal structure at the resonance, inducing a strong optical force and allowing a single particle trapping with a diameter less than 100 nm. The device turns out very useful for novel biomedical applications, such as proteomics and oncology.