Light as a driver for nanomachines

Light as a driver for nanomachines

Engineers from Yale University, United States, have shown that it is possible to harness the force of light to drive nanomachines. The result of their research could lead to fully optical mechanical devices made of nano-sized photonic circuits.

The work, published in the journal Nature, successfully combines two important emerging fields of research: nanophotonics and nanomechanics; and it could make it possible to manufacture tiny mechanical and optical parts on the same silicon chip.

Although the force exerted by photons is too weak to be felt in everyday life, it can be greatly enhanced by concentrating the light into nano-sized photonic circuits.

Until now, the force of light has only been used to move small objects using a technique called "optical tweezers." These tweezers work by catching micrometer-sized objects near the focus of a laser beam. The technique allows grabbing objects and moving them to another place using only light. Now, Hong Tang and his colleagues have taken this concept a step further, showing that optical forces can be harnessed to move an entire semiconductor device.

The researchers showed that as concentrated light passes through a separate nanomechanical photon resonator, which also acts as a waveguide for the light, the resonator folds. The optical force causing this displacement can be measured as the change in coupling between the resonator and the underlying substrate. The force (which can be as high as 8 pN per micrometer per milliwatt) would be large enough to move nanoscale machinery on a chip, Tang and his colleagues note.

The optical force produced by the new method actually acts perpendicular to the direction of the light beam; something different from what happened in previous systems, in which the optical force was parallel to the direction of light propagation. This means that the configuration of mirrors or cavities, difficult to implement in systems at scale of integrated circuits, is no longer necessary. And that's not all: the force of light is inherently fast and can therefore direct nanomechanical devices at very high frequencies, possibly exceeding the current milestone of a few gigahertz, Tang notes.

According to him, the magnitude of the force is roughly the same size as other forces commonly used to actuate nanodevices, such as magnetic or electrostatic forces, but without the need for external fields. "All this implies that, in the near future, it will be possible to develop a fully photonic nanoelectromechanical system, with integrated optical detection and activation." On the other hand, all optical devices would also require much less energy than those that use electrons.

Source: Nanotech Web