Researchers have developed a method to simultaneously control diverse optical properties of dielectric waveguides by using a two-layer coating, each layer with a near-zero thickness and weight.
Waveguides carry electromagnetic or optical signals from the source to the device — an antenna or other microwave, millimeter-wave, or terahertz device. Waveguides are an essential component in any electromagnetic or optical system, but they are often overlooked because much of the focus has been on the devices themselves and not the waveguides.
Metasurface coatings allow researchers to shrink the diameter of waveguides and control the waveguiding characteristics with unprecedented flexibility. A material was developed that is so thin it is almost two-dimensional, with characteristics that manipulate and enhance properties of the waveguide.
Two conformal coatings were developed and tested — one for guiding the signal, and one to cloak the waveguide. The coatings were created by judiciously engineering the patterning on the surfaces to enable new and transformative waveguide functionality. The coatings are applied to a rod-shaped Teflon waveguide with the guiding layer touching the Teflon and the cloaking layer on the outside.
This quasi-two-dimensional conformal coating that is configured as a cloaking material can solve the crosstalk and blockage problem. Dielectric waveguides are not usually used singly, but in bundles. Unfortunately, conventional waveguides leak, allowing the signal from one waveguide to interfere with those located nearby.
The effectiveness of the artificial coating can be well maintained for waveguide bends by properly matching the dispersion properties of the metasurface unit cells. Although the coating can be applied to a bend in the waveguide, the waveguide cannot be bent after the coating is applied.
Improving the properties of the waveguide to carefully control polarization and other attributes allows the waveguides to be smaller, and alleviating crosstalk allows these smaller waveguides to be more closely bundled. Smaller waveguides more closely bundled could lead to increased miniaturization.