Metasurfaces are two-dimensional counterparts to metamaterials, artificial materials with unusual properties. These specially prepared surfaces with artificially generated patterns can change the propagation of electromagnetic waves across the entire wavelength spectrum and offer a variety of fascinatingly innovative and diverse applications.

Although the journey of metamaterials began with metallic-dielectric systems, metasurfaces are now fully dielectric and play a crucial role in applications related to optoelectronic devices such as solar cells and light-emitting diodes (LEDs), improving their efficiency through a mere surface effect.

Student researchers led by Professor R. Vijaya at the Photonics Laboratory of the Indian Institute of Technology Kanpur in India recently used a low-cost soft lithography technique to fabricate dielectric metasurfaces consisting of two complementary shapes of nanodimples and nanobumps on a flexible polymer substrate.

The work entitled “Control of visible‑range transmission and reflection haze by varying pattern size, shape and depth in flexible metasurfaces” was published in Limits of optoelectronics.

As a master pattern, the researchers used a low-cost photonic crystal fabricated by self-assembly with nanometric feature sizes. The doubly economical approach thus delivers metasurfaces that are thin, flexible, patterned and easily laminated to any smooth surface.

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

Haze scattering effects are visible in the haze patch surrounding the transmitted/reflected beam, and simply controlling their extent can increase the amount of light absorbed in solar cells or extracted in LEDs. Method-based simulation results also support the experimental results.