Towards cavity optomechanics with integrated multi-element mechanical resonators

Abstract

Cavity optomechanics describes the interaction between an intracavity light field and a mechanical resonator. This mutual coupling allows for a means to optically control mechanical motion down to the quantum regime. Using an optomechanical device to observe non-linear quantum effects, such as direct generation of non-classical states, requires the strong single photon-phonon coupling regime, which is yet to be experimentally realized for chip-based devices. Coupling light to the collective motion of an array of highly reflective mechanical resonators has been predicted to increase the coupling strength and is therefore a promising way forward in achieving this goal. In this thesis, I present the first steps towards realizing cavity optomechanics with multielement membrane-type resonators fabricated from an AlGaAs heterostructure. The optical and mechanical properties of single- and double-layer resonators are characterized, showing resonance frequencies in the 100 kHz regime and room temperature mechanical quality factors of 10^4 at high vacuum. The reflectivity of the AlGaAs heterostructure is measured to be > 95 % at telecom wavelengths. The membrane devices are subsequently inserted as the back mirror of a 10 mm long Fabry-Pèrot-type cavity. This membrane-at-the-edge geometry shows a cavity linewidth of 6.38(8) MHz, corresponding to a finesse of 2370(30). Finally, an experimental setup for characterizing optomechanical properties is discussed, and its performance is analyzed in terms of cavity mirror impedance mismatch and membrane clipping loss.