Optimized light-matter interaction and defect hole placement in photonic crystal cavity sensors

Photonic crystal slab cavities were investigated for increased light-matter interaction based on selective placement of sublattice hole sized defect holes inside L3 cavities. A multiple-hole defect (MHD) consisting of three defect holes placed in the regions of highest cavity mode field intensity were demonstrated through finite-difference time-domain simulations and experiments to exhibit the strongest light-matter interaction without introducing significant scattering losses. Compared to an L3 cavity without defect holes, these strategically designed three-hole MHD cavities presented higher quality factor and more than double the resonance wavelength shift upon exposure to a thin oxide and two small chemical molecules.