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  • Nanodiamonds Optically Levitated
Aug 2013
ROCHESTER, N.Y., Aug. 13, 2013 — A technique using two lasers — one to trap nanodiamonds in space and the other to cause them to emit light at given frequencies — could prove invaluable in high-sensitivity nanoscale force sensing.

Researchers at the University of Rochester, led by assistant professor of optics Nick Vamivakas, demonstrated photoluminescence from the optically levitated diamonds and showed that it is possible to levitate those as small as 100 nm in free space.

“Now that we have shown we can levitate nanodiamonds and measure photoluminescence from defects inside the diamonds, we can start considering systems that could have applications in the field of quantum information and computing,” Vamivakas said.

University of Rochester researchers demonstrate photoluminescence from optically levitated nanodiamonds. The research could allow researchers to test fundamental physics questions related to quantum mechanics as well as provide a tool to perform high-sensitivity nanoscale force sensing. Photos courtesy of J. Adam Fenster/University of Rochester.

Possible avenues of interest include optomechanical resonators, allowing for the creation of Schrödinger cat states (macroscopic systems that are in two quantum states at once). Resonators also could be used as extremely sensitive sensors of forces; e.g., to measure tiny displacements in the positions of metal plates or mirrors in configurations used in microchips and to better understand friction on the nanoscale.

University of Rochester optics professor Nick Vamivakas, right, and physics Ph.D. candidate Levi Neukich perform experiments with optically levitated nanodiamonds.

The light emitted by the nanodiamonds is the result of photoluminescence. The defects inside the nanodiamonds absorb photons from a second laser, which excites the system and changes the spin. The system then relaxes, and other photons are emitted (a process known as optical pumping).

To position the 100-nm diamonds in the correct spot, an aerosol containing dissolved nanodiamonds is sprayed into a chamber where the laser is focused. The diamonds are attracted to this focus point and become trapped.

Graduate student Levi Neukirch said that sometimes “it takes a couple of squirts, and in a few minutes, we have a trapped nanodiamond; other times, I can be here for half an hour before any diamond gets caught. Once a diamond wanders into the trap, we can hold it for hours.”

The research was published in Optics Letters.

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laser trapping
A technique for confining atoms, molecules or small particles within one or more laser beams. This can be accomplished through the use of a single focused beam or multiple intersecting beams. With a single focused beam, the matter is confined to the laser beam's focal area. In the case of multiple intersecting beams, the matter is confined to the area of intersection because of the combined cooling effect of the beams. Also called optical trapping.
optical pumping
The process whereby the number of atoms or atomic systems in a set of energy levels is changed by the absorption of light that falls on the material. This process raises the atoms to specific higher energy levels and may result in a population inversion between certain intermediate levels. The optical pumping of an optical medium within a laser cavity is one of the fundamental processes involved in the generation of a beam.
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