EPFL doctorate Award 2014 - Emanuel Gavartin

Mechanical systems at the nano-scale are increasingly used both for fundamental studies and applications, for example for sensing small forces, masses or charges. A promising approach to readout and control these systems is to use cavity optomechanics, which is a recently realized technique coupling a mechanical oscillator to an optical cavity.
In this thesis we envisioned, modeled, fabricated and characterized a novel integrated hybrid optonanomechanical device. The hybrid integration allowed specific optimization of both the optical and mechanical systems, thus leading to an excellent force sensitivity of the robust on-chip device.
With our device we demonstrated ultra-sensitive resonant and off-resonant optomechanical control of our nanomechanical sensor. By implementing a feedback cooling scheme with our system, we have shown a 30-fold reduction of the acquisition time required to detect incoherent forces, reaching atto-Newton resolution at the minute-scale at room temperature. By successfully implementing our system in a cryogenic environment, we could improve its force sensitivity even further.
We have also proposed and implemented a non-invasive, off-resonant optomechanical stabilization scheme that allows to suppress the excessive frequency noise in our system. We were able to stabilize our system to its thermodynamic limit, restoring its full detection capabilities.
This work has important consequences for ultra-sensitive microscopy and quantum sensing.