At the time of the discovery, in the laboratories at CUDOS - the Centre for Ultrahigh Bandwidth Devices for Optical Systems - Dr Christelle Monat and Dr Christian Grillet were assisting PhD student Bill Corcoran with experiments on slow light, itself a very novel and surprising phenomenon, say the researchers.
“When I saw the green light on the camera, I was extremely puzzled” said Dr Grillet of the University of Sydney.
“We were using infrared light, not green. And besides, silicon does not transmit light at that wavelength!” And, Dr Monat’s response at the time - “I didn’t believe the camera. I had to look with my own eyes. It was as strange as seeing a house-brick suddenly emit light.”
The effect was real, however, and was published in the journal Nature Photonics this week. Their infrared laser was being converted to green light – light of higher energy – in a process known as third harmonic generation.
Asked about the potential of this discovery, Dr Monat says: “One could imagine that a small green light indicator could help users of numerous Internet applications. This could be used to immediately inform companies such as Skype of a problem in the clarity of their connections, thereby allowing them to fix this in real-time, all without the end-user even noticing.”
The researchers work in a field known as photonics and they say that converting infrared to green light adds another important tool to the impressive suite of capabilities of silicon, already the material of choice for the micro-electronics industry.
“Being able to control light on a chip, along wires no wider than one hundredth of the width of a human hair, represents the first step to realise all sorts of operations with significantly better performance than electronics alone,” Dr Monat explains.
“And if we can do that in silicon, even more complex and exciting architectures become possible by integrating and marrying both the photonic and electronic worlds.”
The research team’s paper, Green light emission in silicon through slow-light enhanced third-harmonic generation in slow light photonic-crystal waveguides, was published on-line in Nature Photonics on 22 March 2009.