Compact photonic crystal disk cavity optimized using the gentle confinement method and boundary design

A compact, novel photonic crystal cavity aimed at applications with strict area limitations is presented. Optimization shows that the gentle confinement method previously used for line-defect cavities can be applied to more limited geometries. It also shows that it is paramount to consider the boundary region to minimize in-plane losses. The investigation show that a near optimum boundary thickness can be found by considering the boundary region as a Fabry-Pérot resonator. This optimization strategy is shown to be deterministic in terms of resonance wavelength. For an optimized air-clad, silicon cavity, finite-difference time-domain simulations give Q-values as high as 75,000 which is comparable to other photonic crystal cavities of similar size.