It involves layers of thin material whose refractive index changes by up to 60%.
“Unfortunately, it is very difficult to tune refractive index with electric fields,” said researcher Linyou Cao. “Previous techniques could only change the index for visible light by between 0.1 and 1% at the maximum.”
The layers very thin, made from transition metal dichalcogenide – specifically molybdenum sulphide, tungsten sulphide and tungsten selenide.
“Using this technique, we achieved significant, tunable changes in the index within the red range of the visible spectrum,” said Cao.
The changes are dynamic, and can be made billions of times per second. “This technique may provide capabilities to control the amplitude and phase of light pixel by pixel in a way as fast as modern computers,” said Yiling Yu, lead author of ‘Giant gating tunability of optical refractive index in transition metal dichalcogenide monolayers‘ published in Nano Letters.
“This is only a first step,” said Cao. “We think we can optimize the technique to achieve even larger changes in the refractive index. And we also plan to explore whether this could work at other wavelengths in the visual spectrum.”