July 15, 2009--Belgian researchers--at the University of Ghent (Ghent) and the nanoelectronics research center IMEC (Leuven)--have demonstrated repulsive and attractive nanophotonic forces that depend on the spatial distribution of the light used. These fundamental research results could have major consequences for telecommunications and optical signal processing.
Photon impulse is usually considered to be relatively weak--unless you are talking about nanoscale dimensions. When light is confined to very small cross-sections and large gradients exist in the spatial field distribution of the light, the optical gradient force induced per photon increases dramatically.
Using advanced fabrication technologies, including deep ultraviolet (DUV) lithography and critical-point-drying, the researchers created two parallel waveguides on a silicon-on-insulator chip. The waveguides are freestanding, acting as movable strings. They have a width of 445nm, a height of 220nm, a length of approximately 25µm and they are separated by a 220nm gap.
By sending laser light through the waveguides the team was able to generate optical forces between them. Depending on the spatial distribution of the light (both in amplitude and phase) the strings were attracting or repulsing each other. The repulsive force that had never been demonstrated before makes this experiment of fundamental scientific importance.
The experiment might eventually have a major impact to achieve very high speed telecommunication for optical forces provide an interesting option for implementing all-optical signal processing functions on a chip. All-optical routing is one of the key challenges in developing faster communication networks (such as the internet) and the new technique opens up new routes towards solutions for this bottleneck.
The detailed experimental results will be published in the August issue of the journal Nature Nanotechnology.
For more information see the paper, Tunable optical forces between nanophotonic waveguides, in the advance online issue of Nature Nanotechnology. See also the websites for the University of Ghent and IMEC.
