Tuneable optical coatings

Researchers at the University of Oxford have identified and used a new class of chalcogenide glass materials in optical coatings which have potential applications across a broad range of optical components.

These new optical coatings provide a continuously tuneable refractive index and incredibly low losses. Further, the stack arrangement required to use this new class of chalcogenide glass materials is significantly less complex than the arrangement required for use with phase change materials.

Optical coatings, which are easy-to-manufacture multi-layered stacks of dielectric and metallic thin films, are used in a broad range of different components of devices including data storage mediums, lenses and displays.

Photonic components such as spatial light modulators can also make use of these stacks. Such optical coatings utilise the principle of thin film interference, i.e. phase driven constructive and destructive interference of light waves, to enable a multitude of optical effects.

Often thick optical coatings are required in order to achieve desired optical effects in a device. This means that the process of applying optical coatings can be material intensive. Further, such coatings are passive, meaning they lack tunability due to their static material properties, which limits their usefulness in many potential applications such as solid-state displays and smart glasses.

In recent years, the creation and manipulation of colour reflected off a surface by changing the refractive index of ultra-thin functional layers has been realised through use of phase change materials (PCMs). Optical coatings and devices can be designed with ultra-thin film structures such that white light is reflected as red, green or blue.

Having PCMs in these thin film structures means that the light reflected in the displays can be adapted and tuned on demand. Whilst PCM’s lead the way in tuneable optical coatings, such coatings often require a more complex stack arrangement and can have high optical losses associated with them, which is not ideal in many scenarios where transmission/reflection efficiency is of crucial importance.

With this in mind, researchers at the University of Oxford have identified a new class of chalcogenide glass materials, with highly tuneable properties, reduced stack complexity and applicability across a broad range of devices. This enables components to be manufactured which are thinner and exhibit lower losses than in existing devices. In addition, the optical properties can be continuously tuned, in contrast to many existing devices which are restricted to a limited number of different optical states.

Patent protection

This novel technology is the subject of a patent application. Oxford University Innovation is now seeking commercial partners to adopt the new technology and support its future development.

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