Affordable, flexible metasurfaces enhance the performance of optoelectronic devices

Metasurfaces are the two-dimensional equivalents of metamaterials, artificial materials with extraordinary properties. With a variety of fascinatingly innovative and diverse applications, these specially prepared surfaces with engineering patterns can modify the propagation of electromagnetic waves across the entire wavelength spectrum.

Although the origins of metamaterials lie in metal-dielectric systems, metasurfaces are now becoming fully dielectric and are playing a key role in optoelectronic device applications such as solar cells and light-emitting diodes (LEDs), increasing their efficiency through surface effect alone.

Student researchers led by Professor R. Vijaya of the Photonics Laboratory at the Indian Institute of Technology in Kanpur, India, recently used an inexpensive soft lithography technique to fabricate dielectric metasurfaces with two complementary shapes of nano-cavities and nano-convexities on a flexible polymer substrate.

The paper, titled “Control of visible transmission and reflection haze by varying the size, shape, and depth of the pattern on flexible metasurfaces,” was published in The Frontiers of Optoelectronics.

The researchers used a low-cost self-assembled photonic crystal with nanometer-sized features as the master pattern. This doubly cost-effective approach yields metasurfaces that are thin, flexible, patterned, and easy to laminate to any smooth surface.

Using samples of different sizes and pattern depths, their experiments on diffuse and total reflection and transmission showed that the haze from these samples could be controlled over the entire visible range. This is useful for improving the performance of optoelectronic devices where the efficiency of optical-to-electrical conversion is limited due to the linear direction of light propagation.

The fog scattering effects will be visible in the fog patch surrounding the transmitted/reflected beam, and easy control of their range can increase the amount of light absorbed by the solar cells or extracted by the LEDs. The simulation results based on the methods also confirm the experimental findings.