Though all light particles
have force, you needn’t worry about dodging moonbeams at night.
Even all the photons streaming to Earth during the day could never
hope to budge something as small a hair, let alone a human body. On a
much smaller level, though, where the wavelength of the light can be
matched or represented in small multiples by microscopic devices,
these effects can be realized and measured.
Cornell University have managed to harness
the sucking power of a beam of light to create what could be used
as an optical switch or filter from two resonating rings and a small
straight wave guide tuned to a frequency of infrared light. The rings
themselves resemble four-spoke wheels, mounted like semi-tractor
tires on one end of a rear axle. The silicon nitride rings have a
diameter of 30 microns and are mounted 190 nanometers apart. The
waveguide part of the ring, or the rubber part of our tractor tires,
measures a scant 3 microns.
When light passes through a
waveguide that is narrower than the wavelength of the light, some or
most of the beam’s energy will escape the waveguide and this energy
exerts an attractive force on objects near it. With this property in
mind, the researchers mounted the resonating waveguides in close
proximity so that their escaping energy would attract each other. By
using this method, the group was able to expand or contract the
distance between the waveguides by as much as 12 nanometers –
enough to change the optical properties of the device creating what
could be used as an optical switch or filter for other beams of light
passed through the space.
This effect may also be useful in
the field of micro-electromechanical
systems, where forces at the subatomic and quantum levels, such
as the Casimir force, create sticky situations for tiny mechanical
parts. By reversing the phase of one of the resonating rings, the
forces which once pulled the rings together instead push them apart.
Controlled, this could help fight “stiction” as it has been