Photonic circuits can allow lightto be tightly confined on a chip. A clever experiment reveals how this process can be exploited to create optical forces that drive a nanoscale mechanical oscillator. In the 1970s, Arthur Ashkin at Bell Laboratories showed that the force that light exerts on an object - the radiation pressure force -can be used to trap particles. This discovery has led to a revolution in the use of lasers to trap objects ranging from atoms to biological cells. With 'optical tweezers', for example, a laser beam is focused tightly on the surface of an object, and a spatial variation in the optical intensity creates a gradient force that causes the object to be attracted to the centre of the beam, where the intensity is highest. On page 480 of this issue, Li et al. describe how they have used nanoscale photonic waveguides on a silicon chip to exert optical gradient forces on a nanomechanical oscillator - a first step towards unifying nanophotonics and nanomechanics.
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