Optomechanics and Levitation
The motivations behind the huge interest in developing quantum opto-mechanical systems are varied. On a technological level, these systems are pushing the limits of high precision sensing for the detection of small forces, displacements, masses and accelerations which when packaged appropriately provide sought-after commercial applications. On a more fundamental level, quantum opto-mechanics focuses on manipulating and detecting of the mechanical motion in the quantum regime using light, thereby allowing for the generation non-classical states of the mechanical oscillator.
Optical sorting of ultrabright nanodiamonds
Description: In recent years, fluorescent nanodiamonds have become increasingly popular as biomarkers and imaging agents, and many potential applications have been suggested or are already being pursued [1, 2]. Nanodiamonds are highly biocompatible and their surface chemistry is highly controllable. They can host a large number of colour centres which exhibits bright and stable fluorescence. Protected by the diamond matrix, these colour centres usually preserve their characteristic quantum optical properties even at room temperature. Optical tweezers usually rely on the interaction of light and the polarizability of the nanoparticle. We here want to exploit electronic resonances of optical centres embedded in solid-state matrix to enhance the optical forces . We explore this effect in nanocrystals with a high concentration of active centers. It has been shown  that if the atoms are close enough to each other, they can act cooperatively, enhancing further the optical forces. We are currently investigating the resonant scattering optical force (radiation pressure) on dense SiV and NV nanodiamonds in a microfluidic chip setup.
 M. L. Juan & al., Nat. Phys. 13, 241–245 (2017)
 B. Prasanna Venkatesh & al., Phys. Rev. Lett. 120, 033602 (2018)
Contact: James White, Cyril Laplane, Thomas Volz
Optical tweezers in microfluidic chip for characterization of nanoparticles in wet environment
Description: We can optically trap and characterize a wide range of nanoparticles in a microfluidic chip. This setup allows us to trap a single nanoparticle and to flush the rest of the particles out of the channel, which is particularly interesting for long measurements. We can as well change entirely the liquid environment while keeping the particle trapped, thus studying the dynamics of the nanoparticles in different wet environments.
Contact: Cyril Laplane, Thomas Volz
Optically levitated nanocrystals for sensing
Description: We are also pursuing the study of the dipole force (tweezer part) on bright nanodiamonds and rare-earth ions doped nanocrystals. Applying the powerful toolbox of atomic physics, we will be able to regime new regime of control for quantum optomechanics experiments. These studies might help us understand collective effects in the solid-state and help us harvest a relatively new effect for quantum technologies of mesoscopic systems.
Optical levitation in vacuum offers a unique platform for investigating and manipulating particles where the only interactions occurring are between the light field and the particle itself. In addition, the oscillatory motion in the optical trap offers additional modalities for sensing such as for measuring external vibrations. One of the main limitation of optically levitated systems in vaccum is heating due to the trapping field. Rare-earth ions doped nanocrystals are uniquely suited for that purpose. Indeed using laser refrigeration, we can extract heat from the crystal through anti-Stokes fluorescence . Together with the aforementioned ‘atomic’ enhancement we expect to develop the ‘perfect’ quantum system: isolated, cold and highly coherent. Such a mesoscopic quantum system will allow us to investigate the interplay between quantum physics and gravity and probe the frontier between the classical and quantum world.
 A. T. M. Anishur Rahman & P. F. Barker, Nature Phot. 11, 634–638 (2017).
Contact: Reece Roberts, Cyril Laplane, Thomas Volz