Mechanical Systems in the Quantum Regime: Cavity Optomechanics

Physics Colloquium

Speaker: Tobias Kippenberg
When: Jan. 21 2014 17:15
Where: Erwin-Schödinger-Saal, IQOQI

The mutual coupling of optical and mechanical degrees of freedom via radiation pressure has been a subject of interest in the context of quantum limited displacements measurements for gravity wave detection for many decades. Over the past years these radiation pressure “backaction” phenomena have been observed – starting from observations in in high Q optical microresonators – in a variety of micro and nanoscale opto and electro‐mechanical systems. The high Q of the microresonators, not only enhances nonlinear phenomena ‐ such as optical frequency comb generation via the Kerr nonlinearity – but also enhances the radiation pressure interaction. This has allowed the observation of radiation pressure phenomena in an experimental setting and constitute the fast developing research field of cavity quantum optomechanics. I will describe a range of optomechanical phenomena studied using on‐chip optical microresonators, that combine both optical and mechanical degrees of freedom in one and the same device. Radiation pressure back‐action of photons is shown to lead to effective cooling of the mechanical oscillator mode using dynamical backaction. Cooling to the quantum regime is possible using sideband resolved cooling, with passive of cryogenic precooling to ca. 700 mK, which enables cooling the oscillators such that it resides in the quantum ground state more than 1/3 of its time. Increasing the mutual coupling further, it is possible in this regime to observe quantum coherent coupling in which the mechanical and optical mode hybridize and the coupling rate exceeds the mechanical and optical decoherence rate. In this regime the mechanical and optical modes form an optomechanical ‘polariton’. This enables a range of quantum optical experiments, including state transfer from light to mechanics using the phenomenon of optomechanically induced transparency. In addition experiments are described that utilized the optomechanical coupling for highly efficient force measurements using nanomechanical oscillators, as well as elements enabling switching, slowing or advancing of radiation.

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