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abstract: 'We demonstrate a cryogenic optomechanical system comprising a flexible [Si$_3$N$_4$]{} membrane placed at the center of a free-space optical cavity in a 400 mK cryogenic environment. We observe a mechanical quality factor $Q > 4\times 10^6$ for the 261-kHz fundamental drum-head mode of the membrane, and a cavity resonance halfwidth of 60 kHz. The optomechanical system therefore operates in the resolved sideband limit. We monitor the membrane’s thermal motion using a heterodyne optical circuit capable of simultaneously measuring both of the mechanical sidebands, and find that the observed optical spring and damping quantitatively agree with theory. The mechanical sidebands exhibit a Fano lineshape, and to explain this we develop a theory describing heterodyne measurements in the presence of correlated classical laser noise. Finally, we discuss the use of a passive filter cavity to remove classical laser noise, and consider the future requirements for laser cooling this relatively large and low-frequency mechanical element to very near its quantum mechanical ground state.'
address:
- '$^1$Yale University Department of Physics, 217 Prospect St, New Haven, CT 06511, USA'
- '$^2$McGill University Department of Physics, 3600 rue University, Montreal, QC H3A2T8, Canada'
- '$^3$Yale University Department of Applied Physics, 15 Prospect St, 