Master Thesis Defence by Tolga Bagci – Niels Bohr Institute - University of Copenhagen

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Master Thesis Defence by Tolga Bagci

The thesis presented here deals with the optomechanical interaction between a mechanical resonator(membrane) and radiation pressure.

A two color-probing scheme is proposed for reading out the displacement of a membrane sitting inside a high-finesse cavity, in order to eliminate technical noise as a common-mode signal. In pursuit of a long-term goal in which we hope to see quantum correlations between light and a high Q micromechanical resonator cooled down to the ground-state, an experimental work has been carried out to characterize the eigenfrequencies and Q-factors of the vibrational modes for SiN(stoichiometric form) and GaAs membranes. Both thermal spectrum and mechanical ringdown measurements were performed and the results were compared.

The author reports impressive Q-factors(dominantly dependent on clamping loss) for SiN membranes, exceeding 10^6 at room temperature, at frequencies in MHz regime. For the GaAs membrane, measurements yielded Q values exceeding 10^5 in 20 kHz-70 kHz frequency range, including one outstanding mode with a Q-factor of≈10^6 and rendering the possibility for more interesting experiments due to the unique properties of GaAs. The master thesis is rather focused on the characterization measurements on two different SiN membranes which can be regarded as prerequisite steps for our prospective optical experiments with mechanical resonators.