Silicon photonics builds on structures called silicon photonic wires, which carry optical signals from one point to another at the speed of light, with the light trapped inside the wire by total internal reflection. Confining light is one thing, says the team, but manipulating it is another.
Reporting in Nature Photonics, the team says it managed not only to confine light, but also sound in silicon nanowires, with the sound oscillating at 10GHz. According to the team, it realised the sound could not be trapped in the wire by total internal reflection, so the scientists sculpted the environment of the core to make sure any vibrational wave trying to escape it would actually bounce back. Doing so, they confined both light and sound to the same nanoscale waveguide core.
Because they are trapped in a small area, the light and vibrations strongly influence each other: light generates sound and sound shifts the colour of light – a process known as stimulated Brillouin scattering.
This interaction was exploited to amplify specific colours of light and the researchers anticipate this demonstration could open new ways to manipulate optical information; for instance, light could be converted into sonic pulses and back into light – thereby implementing delay lines.
