In its work, a team from Ireland’s Tyndall National Institute and Cork Institute of Technology has developed a custom, artificial material that could improve several nonlinear optical applications. Alongside better internet speeds, the team suggests that thinner lenses could be created for cameras and mobile phones, as could new microscopy tools for biology and medicine.
The approach combines metamaterials consisting of arrays of antennas and a thin film of a nonlinear material. While the antenna array is made from gold and the thin film from indium tin oxide, the team believes the concept could be used with a range of other materials.
The metamaterial is said to have a much stronger optical response than available in natural materials. The strength of nonlinear interaction is measured by the change in the refractive index. Normally, this ranges around 0.001, but the team measured a refractive index change of 2.5 with its metamaterial. The response is also said to occur on picosecond timescales.
Researcher Sebastian Schulz said that, because the nonlinear response of most materials is typically extremely weak, nonlinear optics have rarely been used up to now. “Typical optical systems – are linear. This means the behaviour is independent of the amount of light in the system; if the incident light is doubled, the amount of light exciting the system is doubled. Yet, nonlinear optical systems exist, where the behaviour does depend on the amount of light entering the system. In such systems, depending on the power, light can change colour, direction or even its speed and the team would like to use these effects to manipulate light, for example to imprint data on light to reduce the power consumption of the internet.”