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The light at the end of electronics’ dark tunnel is photonics

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Scientists at Heriot-Watt University are a step closer to replacing electrons with photons, solving the looming speed limit in electronic devices.

According to Dr Marcello Ferrera, an assistant professor in Photonics and Optics at Heriot-Watt, electronics have had such long-term success mainly due to how much smaller devices have become, and how robust they are, even when made from a very limited number of fundamental materials.

These last two features have traditionally been weaknesses in the field of photonics, but Dr Ferrera’s findings could change all that. His team have, for the first time, shown how aluminium zinc oxide (AZO) reacts to light when simultaneously shined with ultra-fast laser pulses of different colours. Since AZO is a compound used in touch-screen technology, the discovery could have an immediate impact for the fabrication of novel photonic components.

The nanophotonics experts used one laser beam to explore the optical properties of thin films of AZO, while two different trains of ultra-fast light, pulsed at two distinct frequencies, or ‘colours’, were shone on the material. The experiments were conducted first by using one colour at a time, and afterwards with the combined use of the two laser sources. The recorded effects, which last for a 10,000th of a billionth of a second, were surprising to say the least.

Dr Ferrera said: “We discovered that we can drastically and reversibly alter the optical properties of the material by using laser light with different colours. Each colour can induce strong and ultra-fast alteration on both the transparency of the material and the speed at which light propagates into it.”

Dr Ferrera also discovered that the induced alterations, which are typically opposite in sign, can be algebraically summed up one to another. If the material becomes more transparent with one colour and more absorptive with the other, it will not show any appreciable alteration when the optical stimuli occur simultaneously. This behaviour could have striking consequences for the design and fabrication of optical computing and telecommunication devices.

“The reason we used AZO is that, although it has been used in electronic devices for years, we have little knowledge about how it could be used in photonics.

“Electronics have almost reached their capacity and potential; our findings represent a remarkable step towards the full miniaturisation of photonic components: this possibility was just ‘science fiction’ few years ago.”

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