Spectra of mechanical cavity modes in distributed Bragg reflector based vertical GaAs resonators

Distributed Bragg reflector based semiconductor resonators constitute paradigmatic systems where cavity optomechanical and optoelectronic phenomena can be simultaneously active in the same device. High GHz range mechanical frequencies and ultrastrong optomechanical couplings are additional attractive features for applications. We report here a detailed spectroscopic study of the fundamental optomechanical resonances of such a device. The existent challenge to study vibrational frequencies that are above the bandwidth of current electronics is solved using a purposely made tandem Fabry-Perot-triple spectrometer. A full theoretical description of the Raman process including electronic, vibrational, and optical confinement is presented to describe the experiments. These results open the path for the demonstration of polariton optomechanical phenomena in these devices.