Keith Huie of Virginia Tech, a Ph.D. student in electrical and computer engineering, is doing research on photonic crystal devices to develop efficient means to control the transmission of light. He explains that in conventional optical waveguides, such as widely used fiber optic cables, the ability to transmit light around tight bends has been literally unfathomable because of the considerable amount of loss radiated as the light travels through the bent fiber. This has been a limiting factor when designing small-scale optical devices, since the waveguide networking consumes most of the viable circuit area. This issue has paved the way for the development of optical waveguides contained within a photonic crystal.
Photonic crystals consist of a periodic array of holes — like a honeycomb — patterned in a substrate, such as a silicon wafer. Due to the periodic arrangement of holes, the photonic crystal is capable of completely prohibiting certain wavelengths of light from propagating through its surrounding substrate material. Wavelengths of light forbidden to enter the substrate define a photonic bandgap. However, light is capable of entering the photonic crystal by patterning "defects" in construction of the crystal array. A defect is a region that disrupts the periodic nature of the patterned geometry. For example, defects arranged to form a line in the crystal, as illustrated in the second figure, establish a path for light to propagate unperturbed through the substrate. This defines a photonic crystal optical waveguide. The advantage of this technology is that photonic crystal waveguides are capable of bending 90 degrees without degrading transmission of an incoming light signal. This is possible since neighboring crystals enclose the defect path, preventing electromagnetic energy from leaking along the peripheries of the waveguide. In contrast, conventional fiber optic cables can only bend about 30 degrees before high radiation losses reduce transmission power to only a few percent.
With the ability to control the flow of light, optical components based on photonic crystal technology could revolutionize the development of next-generation communication systems. This research is still under investigation. Huie’s major professor is Richard Claus