Hi all,
Tomorrow our visitor Patrik Potts will tell us about his work on 'Optical coherent feedback control of a mechanical oscillator'. See below for the abstract. The talk will take place at 2pm in HIT E 41.1 or on Zoom: https://ethz.zoom.us/j/362994444.
Best, Ladina
Optical coherent feedback control of a mechanical oscillator
We present the theoretical description and experimental realization of an optical coherent feedback platform to control the motional state of a nanomechanical membrane in an optical cavity. The coherent feedback loop consists of a light field interacting twice with a mechanical oscillator in different cavity modes. Tuning the optical phase and delay of the feedback loop allows us to control the motional state of the mechanical oscillator, its frequency shift and damping rate, which we use to cool the membrane close to the ground state. In the optimal cooling conditions, we derive an expression for the minimal number of phonons and show that this new technique enables ground state cooling. Experimentally, we show that we can cool the membrane to a state with 4.89 ± 0.14 phonons (480 μK) in a 20 K environment. This lies below the theoretical limit of dynamical backaction cooling in the unresolved sideband regime. The described feedback scheme is very versatile and could be implemented in various optomechanical systems.