Optical sensing of square lattice photonic crystal point-shifted nanocavity for protein adsorption detection

We propose a point-shifted D0 nanocavity formed by locally modulating four central air holes in square lattice photonic crystal for optical sensing application. Three defect modes in this nanocavity, including monopole, whispering-gallery, and dipole modes, are identified in experiments. We also apply a chemical treatment on InGaAsP surface to form a 1-octadecanethiol linking monolayer, which enables the following protein adsorption. In experiments, the wavelength shifts of lasing modes in the D0 nanocavity due to the protein adsorption are observed and agree with the simulation results. This can be a practical tool for label-free molecule detection in biomedical researches. © 2010 American Institute of Physics. doi:10.1063/1.3436550