Quantum-optical trapping of nanodiamonds containing NV centres
thesisposted on 28.03.2022, 02:54 by Reece P. Roberts
Optical trapping offers a non-contact, non-destructive tool for manipulating and handling particles from micron sized particles down to individual atoms with light. One can distinguish two different applications to optical trapping. The first relying on the ability to trap small particles (from tens of nm to tens of μm); and the second one related to the confinement and cooling of atoms or collections of atoms. Until now there has been no system that combines the forces due to both classical trapping and atom trapping as they are usually contained in completely separate parameter regimes even though both of these trapping applications arise from the same force. The force is the result of the interaction of the polarisability of the trapped object, which depends directly on the dipole strength, with the electric field of the trapping laser. In the case of classical trapping, the force acts on an induced dipole caused by the electric field on the object, whereas, in the case of atom trapping the induced dipole arises from the transitions present in the electronic structure. In this way, optically trapped nanoparticles containing embedded optical defects brings about new regimes of trapping and cooling nanoparticles. This new quantum-optical trap allows well established techniques from atom trapping to be applied to the nanoparticles. The result is a quantum-optical trap showing capabilities with much higher trapping strengths and therefore enhanced control for manipulation. The quantum-optical trap also leads to the direct characterisation of the solid state transition properties of the embedded optical defects through force measurements of the trapped nanoparticle. In addition, in the future by applying well established techniques from atom trapping and cold atom physics to the optically trapped particle we can produce a dramatically stronger trap with the potential to cool the nanoparticle centre of mass motion down to its quantum ground state. In this thesis I focused on identifying the trapping forces on the optical defects inside of optically trapped nanoparticles. I developed an experimental setup and procedure to isolate, trap and reliably measure the trapping behaviour of nanoparticles as a platform for investigating the quantum forces on optical defects in nanodiamonds, specifically the quantum force due to the 1042nm metastable transition of the nitrogen vacancy centre.