Exquisite optical control of quantum mechanical oscillators
Optomechanical coupling, the coupling between light and mechanical motion, enables the optical tuning of oscillators with high precision and high frequency. The EU-funded project USOM sought to facilitate ultra-strong optomechanical coupling by exploiting radiation pressure with the ultimate goal of controlling mechanical oscillation at the quantum scale. Researchers also explored, for the first time, opportunities to use plasmonic systems of electromagnetic fields confined to nanoscopic volumes in quantum optomechanical experiments and devices. Reducing system size can optimise coupling strength. Scientists used finite element method (FEM) models to design miniature silica toroidal resonators supported by 'spokes' with very small mass and ultra-low loss. The 2D photonic crystal cavities produced a record-high coupling between optical cavity modes and the motion of acoustic modes (high-frequency mechanical oscillations). The spoke-supported design and low mass enabled radiation pressure cooling of the oscillator mode to the quantum ground state. In the end, researchers were able to demonstrate optical control over the quantum state of motion in the mechanical oscillator and optimise optomechanical function. They then exploited the system in new quantum experimental protocols developed within the scope of the project. Together, the techniques made it possible to cool optomechanical systems to the quantum state. Moreover, these novel methods also permitted the control and read-out of the quantum state of motion in mechanical oscillators. A second line of research resulting in groundbreaking experiments that explored integration of a plasmonic resonator with a nanomechanical oscillator. Plasmonic resonance is a phenomenon of oscillating waves of electron charge density confined to a very, very small space. Scientists employed a plasmonic resonator as a transducer of nanomechanical motion enabling a read-out of the oscillator's thermal motion. USOM contributed pioneering developments in the field of optomechanical coupling and optical control over the quantum ground state of motion of oscillators. The technology and techniques developed within this project will also foster the development of novel devices in fields such as sensing and signal processing.
