Research leads to TV gold

There’s nothing worse for the telly addicts amongst us than sitting down to watch TV and getting an awful glare off the screen, but a simple layer of gold could help to make the glass more transparent say researchers in London.

In flat-screen TVs and light emitting diodes (LEDs) – found in watches and alarm clocks – light is generated within a layer of active material in the glass. This layer traps light, meaning it can only be viewed head-on, and not at other angles. Light is reflected back from the glass at larger angles – instead of passing through it – meaning we see a reflection, rather than the image behind it.

Researchers from King’s College London found that by covering glass with a film of gold, more light can be transmitted through more angles, reducing the amount of light that is reflected back.

“This research could greatly increase output in LEDs, allowing new heights of efficiency to be reached,” said research leader Ryan McCarron, a PhD student from the department of physics. “It may also allow nanoscale light sources for many other applications such as bio and chemical sensing and integrated photonics.”

The research – published in Applied Physics Letters – shows that the interaction of light and electrons can be engineered on the nanoscale. By applying a very thin layer of gold over the glass and controlling the thickness of the thinnest part of the layer, researchers could increase the transmission of light through the glass. This results in light passing through the glass even when it’s not viewed head on – and at greater intensity.

“The gold layer is patterned with a series of parallel lines on the nanoscale, forming a grating,” McCarron told Laboratory News.  “This grating allows light falling upon the gold to become coupled into a surface plasmon polariton; a state of the light which propagates only along the gold surface. This plasmon can transfer to the opposite surface of the gold, where it is quickly decoupled back into light when it encounters a grating feature. This occurs at all incident angles, and so the transmission can continue far beyond the threshold of total internal reflection.”

McCarron explained that the thinnest part of some of the gratings investigated controls a specific resonance within the grating. This means by adjusting this thickness, the wavelength which undergoes the highest transmission can be adjusted, allowing the scientists to tailor our structures for devices of differently coloured emission.

Light extraction beyond total internal reflection using one-dimensional plasmonic crystals