Dynamic plasma/metal/dielectric crystals are able to filter electromagnetic signals in the 100- to 300-GHz range, transmitting desired frequencies at any given moment of time. White light impinging on the crystals symbolizes broadband mm-wave signals that are filtered by the crystals, allowing only narrowband radiation (shown as red, green, or blue beams) to exit the crystal. (Image: University of Illinois)

Communications systems using higher-frequency electromagnetic waves can transfer more data at faster rates but lack network components to handle these higher bandwidths. Sugar-cubesized blocks of an electromagnetic material can rapidly switch functionality to perform the varied tasks needed to support a network with carrier frequencies of over 100 GHz. The miniscule-scale architecture concealed within the sugar cube blocks generates multiple channels operating simultaneously at different frequencies. Basically, this allows multiple conversations to occur over the same network, which is the heart of highspeed wireless communications.

Plasma is critical for swiftly switching between functions and frequencies but previous plasma-based electromagnetic crystals were much too large to operate at high frequencies. The key lies in creating a structure with spacing between the plasma and metal columns as small as the wavelength of radiation being manipulated. The wavelength of electromagnetic waves shortens as the frequency and bandwidth increase. To realize crystals of high bandwidth operating at frequencies above 100 GHz, a small-scale design is required.

Researchers developed a 3D-printed scaffold that served as a negative of the desired network. A polymer was poured in and once set, microcapillaries 0.3 millimeters in diameter were filled with plasma, metal, or a dielectric gas. Using this replica-molding technique, it took nearly five years to perfect the dimensions and spacings of the microcapillaries in the woodpile-like lattice. The material observed resonance spanning the 100- to 300-GHz frequency region.

Rapid changes in the electromagnetic characteristics of these crystals — such as switching between reflecting or transmitting signals — could be achieved by simply turning on or off a few plasma columns. Such a capability shows the utility of such a dynamic and energy-efficient device for communications.

The crystal could be tuned to respond to the resonances of specific molecules, e.g., atmospheric pollutants, and be used as a highly sensitive detector.

For more information, contact Lois Yoksoulian at This email address is being protected from spambots. You need JavaScript enabled to view it.; 217-244-2788.