April 22, 2013
New Nanoscale Router Converts and Directs Subwavelength Signals
|Harvard physicists have found a new way to precisely manipulate light at the subwavelength scale without damaging a signal that could carry data. This opens the door to a new generation of on-chip optical interconnects that can efficiently funnel information from optical to electronic devices.|
The findings, published in the journal Science, offer a new way to precisely manipulate light at the subwavelength scale without damaging a signal that could carry data. This opens the door to a new generation of on-chip optical interconnects that can efficiently funnel information from optical to electronic devices.
"If you want to send a data signal around on a tiny chip with lots of components, then you need to be able to precisely control where it's going," says co-lead author Balthasar Müller, a graduate student at the Harvard School of Engineering and Applied Sciences (SEAS). "If you don't control it well, information will be lost. Directivity is such an important factor."
The coupler transforms incoming light into a wave called a surface plasmon polariton, a surface ripple in the sea of electrons that exists inside metals.
These images, taken with a near-field scanning optical microscope, show plasmonic waves propagating across the surface of the coupler. In the central image, linearly polarized light is captured and converted into waves that travel both left and right. In the left image, left-hand circularly polarized light is routed only to the left; in the right image, right-hand circularly polarized light is routed only to the right. Images Source: Jiao Lin and Balthasar Müller.
The coupler consists of a thin sheet of gold, peppered with tiny perforations. But the precise pattern of these slits, arranged rather like herringbones, is where the genius lies.
"The go-to solution until now has been a series of parallel grooves known as a grating, which does the trick but loses a large portion of the signal in the process," says principal investigator Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at Harvard SEAS. "Now perhaps the go-to solution will be our structure. It makes it possible to control the direction of signals in a very simple and elegant way."
|An electron micrograph shows the nanoscale perforations at the surface of the plasmonic coupler.|
Because the new structure is so small—each repeating unit of the pattern is smaller than the wavelength of visible light—the researchers believe it should be easy to incorporate the design into novel technologies, such as flat optics.
Capasso spoke excitedly about the possibilities for incorporating the new coupler into future high-speed information networks that may combine nanoscale electronics with optical and plasmonic elements on a single microchip.
SOURCE University of Harvard
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Topics - Balthasar Müller , Circular polarization , Federico Capasso , Harvard University , nanoscale router , nanotechnology , Polarization , subwavelength