The study of mechanical systems in their quantum ground state motivates the development of novel optomechanical resonators with frequencies higher than a few GHz. In this particular frequency range, standard cryogenic techniques become sufficient to reach the quantum regime without relying on additional sideband optical cooling.

Recently, we presented GaAs/AlAs pillar microcavities as new optomechanical resonators performing in the unprecedented 18-100 GHz mechanical frequency range, showing highly promising features such as state-of-the-art quality factor-frequency products. We explore novel phonon confinement strategies as well as innovative measuring techniques.