Smart phone waveguides: Laser-etched displays

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  • Published: Jul 1, 2014
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Smart phone waveguides: Laser-etched displays

No mist in Gorilla Glass

An Invisible Waveguide (Pathway For Light) Being Written Via Laser Into A Smartphone’s Display Glass. The Waveguide Is A Horizontal Line From The Left Side Of The Screen, But It Cannot Be Seen With The Naked Eye. Credit: Optics Express.

The first laser-written light-guiding systems have been developed by researchers from Montreal and the New York-based company Corning Incorporated with the aim of etching waveguides into the glass screen of a smart phone. The development could allow layers of sensors, for health monitoring (temperature, blood glucose, even genetic testing), environmental testing and other applications to be incorporated transparently into the screen without adding to the phone's form factor.

The researchers have used their new technology to build two completely transparent systems - a temperature sensor and a new system for authenticating a smart phone using infrared light - into the tough alkali aluminosilicate "Gorilla Glass", manufactured by Corning, and currently used for most models of smart phone and many laptop and tablet computers from the major hardware manufacturers.

In addition to biomedical sensors, the technology could also eventually allow computing devices to be embedded into any glass surface, such as windows or tabletops, creating transparent touch screens of the kind occasionally seen in science fiction movies and television shows, the researchers say. Raman Kashyap, a professor of electrical engineering and engineering physics at Polytechnique Montreal in Canada, suggests that the development of the technology is like opening a new box of tricks. "Now that the technique is viable, it's up to people to invent new uses for it," he says.

Smooth waveguides

To make their transparent temperature-sensing and phone-authentication systems, the researchers turned to photonics. The researchers used a laser to etch out waveguides into the glass, which can then channel light, much as wires channel electrons. Team member Jerome Lapointe of Polytechnique Montreal explains that these photonic waveguides are the nearest to perfect that have been made using lasers; they are ten times better at minimizing light leakage than previous waveguides. The internal stress and low number of irregularities in Gorilla Glass helps considerably in this regard.

The approach is much cheaper and avoids the complex processes involved in photolithography, Lapointe says. Moreover conventional photolithography restricts waveguides to the surface of the glass. But using lasers enables the researchers to make waveguides at any depth with the glass itself, allowing them to create many applications, one on top of each other. Such layering within the glass itself paves the way for more compact devices.

Patented proofs of principle

In their first proof of principle, the team built a known temperature sensor that simply consists of a straight and a curved waveguide. As the glass heats up, it expands and the path length of the waveguides changes. By measuring how the light that emerges from one waveguide interferes with light from the other, the device can measure temperature the temperature of anything with which it comes into contact.

The second demonstration, the authentication system, uses waveguides with holes at various locations. The light that escapes through those holes creates a pattern that is unique to their arrangement. The idea is that each phone would have its own unique pattern, like a fingerprint, which could then be read by an infrared detector to confirm the identity of the phone as an additional layer of security for making financial transactions using smart phones. Both applications are being patented and the collaborators are now seeking commercial partners.

Related Links

Optics Express, 2014, 22, 15473-15483: "Making Smart Phones Smarter with Photonics"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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