Wednesday 25 February 2015

Interaction between Light and Sound in Nanoscale Waveguide

Interaction between Light & Sound – Nanoscale Area

Scientists of Belgium from Ghent University and Nano-electronics research institute, Imec, had a demonstration on the interaction between light and sound in a nanoscale area and their discovery published in the Nature Photonics indicate that the physics of light matter coupling at the level of nanoscale, has paved the way for enhanced signal process on mass producible silicon photonic chips.

The field of silicon in the last decade has attracted increased attention as a driver of lab-on-a-chip biosensors as well as of faster-than-electronics communication between the computer chips. The technology has been built on nanoscale structures which are called silicon photonic wires that are roughly hundred times narrower than human hair and these nanowires tend to carry optical signal from one point to another at the speed of light and are developed with the same technology to fabricate electronic circuitry.

 The wires tends to operate since light moves slower in the silicon core than the surrounding air and glass and due to the trapped light in the wire by the phenomenon of total internal reflection.

Sound Moves Quicker in Silicon Wires 

Confining light simply is one thing though manipulating it is another and the problem is that one light beam cannot change easily the properties of another. It is here that the light matter interaction is in focus which enables some photons to control the other photons.

Researchers from Imec as well as the Photonics Research Group of Ghent University portrayed a peculiar form of light matter interaction and managed to confine light as well as sound to the silicon nanowires where the sound oscillates ten billion times per second which is far more rapid that human ears can hear. They realized that the sound cannot remain trapped in the wire by total internal reflection and unlike light; sound tends to move much quicker in the silicon core than the surrounding air and glass.

The scientistsframed the environment of the core in order to make sure any vibrational wave intending to escape it would eventually bounce back and in doing so, they confined light as well as sound to the same nanoscale waveguide core, a first observation.

Light & Vibration Influence Each Other 

Light and vibrations strongly influenced each other when trapped in an incredibly small area, where light tends to generate sound and sound shifts the colour of light which is a process known as stimulated Brillouin scattering.

They exploited the interaction in order to amplify specific colour of light, anticipating that the demonstration would open up new ways in manipulating optical information such as light pulses could be converted into sonic pulses and back into light, by implementing the much needed delay lines.

Moreover the researchers are expecting that the similar techniques could also be applied to even smaller entities like viruses and DNA since these particles tend to have unique acoustic vibration which could be used to probe their global structure.

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