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 104 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-atthe- 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.