'Lossless' metamaterial could boost efficiency of lasers

1 min read

Engineers at the University of California San Diego have developed a material that could reduce signal losses in plasmonic metamaterials. According to the researchers, the advance has the potential to boost the efficiency of various light-based technologies including fibre optic communication systems, lasers and photovoltaics.

Plasmonic metamaterials are materials engineered at the nanoscale to control light but they typically contain metals that absorb energy from light and convert it into heat. As a result, part of the optical signal gets wasted, lowering the efficiency.

In a recent study, a team of photonics researchers demonstrated a way to make up for these losses by incorporating a semiconductor which emits light.

"We're offsetting the loss introduced by the metal with gain from the semiconductor. This combination theoretically could result in zero net absorption of the signal – a 'lossless' metamaterial," said postdoctoral scholar Joseph Smalley.

"This is the first material that behaves simultaneously as a metal and a semiconductor. If light is polarised one way, the metamaterial reflects light like a metal, and when light is polarised the other way, the metamaterial absorbs and emits light of a different 'colour' like a semiconductor.”

Researchers created the metamaterial by growing a crystal of indium gallium arsenide phosphide on a substrate.

They then etched narrow trenches into the semiconductor, creating 40nm-wide rows, which they filled with silver to create a pattern of alternating nano-sized stripes of semiconductor and silver.

"Rather than creating a stack of alternating layers, we figured out a way to arrange the materials side by side, keeping the semiconductor material defect-free," explained Smalley.