Ar/Cl-2 etching of GaAs optomechanical microdisks fabricated with positive electroresist

A method to fabricate GaAs microcavities using only a soft mask with an electrolithographic pattern in an inductively coupled plasma etching is presented. A careful characterization of the fabrication process pinpointing the main routes for a smooth device sidewall is discussed. Using the final recipe, optomechanical microdisk resonators are fabricated. The results show very high optical quality factors of Q(opt) > 2 x 10(5), among the largest already reported for dry-etching devices. The final devices are also shown to present high mechanical quality factors and an optomechanical vacuum coupling constant of g(0) = 2 pi x 13.6 kHz enabling self-sustainable mechanical oscillations for an optical input power above 1 mW. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement (AU)