Optical trapping at high vacuum of a nanodiamond containing a nitrogen vacancy centre (NVC) would provide a new test bed for several phenomena in fundamental physics. Progress has been made towards this goal but it has not yet been possible to optically levitated nanodiamonds at pressures below a few mbar. We demonstrated that the problem is the absorption of the trapping light by the nanodiamond, which heats them to destruction (above 800 K) except at pressures above a few mbar where air molecules dissipate the excess heat. Here we solve this problem by showing that milling diamond of 1000 times greater purity creates nanodiamonds that do not heat up even when the optical intensity is raised above 700 GW/m2 below 5 mbar of pressure . The large quantities of high purity nanodiamonds made in this way may also find applications in nanoscale sensing such as magnetometry.
We have also proposed an analytical model to describe the interferometric balanced detection which is commonly used to sensitively measure the position of a levitated nanoparticle .
 AC Frangeskou, ATMA. Rahman, L Gines, S Mandal, OA. Williams, PF Barker, and GW Morley, in press at New Journal of Physics, arXiv:1608.04724 (2016).
 ATMA Rahman, AC Frangeskou, PF Barker & GW Morley, Review of Scientific Instruments 89, 023109 (2018)
Angelo C. Frangeskou, A. T. M. Anishur Rahman, Laia Gines, Soumen Mandal, Oliver A. Williams, Peter F. Barker, and Gavin W. Morley, "Pure nanodiamonds for levitated optomechanics in vacuum
(Conference Presentation)," Proc. SPIE 10723, Optical Trapping and Optical Micromanipulation XV, 1072312 (Presented at SPIE Nanoscience + Engineering: August 21, 2018; Published: 17 September 2018); https://doi.org/10.1117/12.2324867.5836015565001.
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