New Color Filter Relies on Nanostructuring

Restructuring the gratings in a new nanoscale filter can result in the production of white and colored light, researchers at the University of Michigan report in a new scientific study.

The team here has developed an advanced type of color filter, which is made out of nanoscale sheets of metal, which are impossibly thin. Each of these sheets features tiny, precisely-spaced gratings.

Each of these structures acts as a resonator in its own right, trapping and transmitting light of a certain wavelength or color, experts at the university say.

The gratings are made out of stacked materials, in a metal-dielectric-metal configuration, Dielectrics are materials that do not allow for the passing of electricity through them.

“Simply by changing the space between the slits, we can generate different colors. Through nanostructuring, we can render white light any color,” explains UM Department of Electrical Engineering and Computer Science associate professor Jay Guo.

The team published details of its investigations in the August 24 issue of the highly-regarded scientific journal Nature Communications.

The newly-developed technology was used to create the smallest-ever UM logo, which is only 12-by-9 microns. This means that its less than one sixth the width of a human hair.

Displays constructed with the new devices could lose less light, and become more efficient than existing liquid-crystal display (LDC) displays.

The advanced color filters act as polarizers simultaneously, eliminating the need for several polarizer layers, such as those present in conventional LCD.

“Amazingly, we found that even a few slits can already produce well-defined color, which shows its potential for extremely high-resolution display and spectral imaging,” Guo explains.

He adds that, in order for the color filter to produce red light, the gratings need to be places about 360 nanometers away from each other.

Green light is produced at a separation of about 270 nanometers, whereas blue light requires a grating spacing of 225 nanometers.

The Nature Communications paper is entitled “Plasmonic nano-resonators for high resolution color filtering and spectral imaging.”