Discrete Quality-Factor Control in a Side-Coupled Photonic Crystal Microcavity: Evanescent Bloch Tunnelling and the Finite-Cell Correction

This paper investigates a point-defect microcavity side-coupled to a W1 waveguide in a two-dimensional photonic crystal composed of silicon rods immersed in an aqueous analyte. The electromagnetic analysis combines plane-wave expansion with finite-difference time-domain computation. It also describes how the resonance shifts through the transverse-magnetic band gap as the defect-rod radius changes, consistent with first-order perturbation theory for restoring dielectric area to the lattice site.