Fine-tuning of GaAs photonic crystal cavities by digital etching

Optical cavities with quality factors above 2 × 10 5 were realized based on photonic crystal heterostructures in a GaAs membrane. The growth of natural oxide on these structures was investigated by monitoring the resonance wavelength of the cavity over time. A logarithmic time dependence of the oxide thickness was found. Combining surface oxidation over a defined time interval and subsequent oxide removal using a wet chemical treatment, tuning of the resonance wavelength in steps of less than 2 nm was achieved.