Numerical simulation of photonic crystal based nano-resonators on scanning probe tip for enhanced light confinement

摘要

We present the design and finite-difference time-domain (FDTD) simulation of a novel near-field visible light confinement probe operating at wavelength of 635 nm, using nano-resonators embedded within a 2D slab photonic crystal waveguide (PCW). The 2D slab PCW is composed of triangular air holes of diameter 136 nm and lattice constant a = 227 nm etched through 1.2a thickness silicon nitride center slab layer and 0.4a thickness silicon dioxide cladding layers. Center evanescent peak was generated for TE excitation, with additional mode matching been considered to greatly reduce the propagation loss. The air slot inside the PCW center line defect creates the boundary condition for a one-and-a-half wavelength nano Fabry-Perot resonating cavities designed to enhance the light throughput. The dominating travelling modes are blocked by the resonator to remove the side lobes in the near field, with the main lobe size being proportional to the size of the air slot. For air slot width of 45 nm, the sub-wavelength light confinement can achieve 1/15th of the wavelength, which is 1000 times enhancement comparing to that of the metal-coated fiber probe tip.