Disorder-induced resonance shifts in high-index-contrast photonic crystal nanocavities

An optical scattering theory is introduced that predicts significant disorder-induced resonance shifts for photonic crystal nanocavities. These counterintuitive modal frequency shifts stem from the subtle role of local electric fields at perturbed (disordered) high-index-contrast interfaces. Using a representative cavity with a quality factor of 40 000 and an effective mode volume of 0.07 μm³, the cavity mode frequency is found to blueshift by up to several meV---even for nanometer-scale imperfections at the dielectric interface---which is several orders of magnitude larger than the cavity linewidth. These disorder-induced resonance shifts apply to a wide range of fabricated photonic nanostructures and scale approximately with the inverse mode volume.