Thinnest Optical Waveguide - 1 (IMAGE) University of California - San Diego Caption Illustration of a monolayer of tungsten disulfide crystal suspended in air and patterned with a square array of nanoholes. Upon laser excitation, the monolayer crystal emits photoluminescence. A portion of this light couples into the monolayer crystal and is guided along the material. At the nanohole array, periodic modulation in the refractive index causes a small portion of the light to decay out of the plane of the material, allowing the light to be observed as guided mode resonance. Credit Cubukcu lab Usage Restrictions Please credit: Cubukcu lab License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.