Optical Metasurfaces Replace Glass Lenses

Glass lenses are used wherever light needs to be specifically bundled, scattered, or focused. The growing demand for smaller, lighter, and more powerful optical systems is pushing traditional glass lenses to their limits: They require installation space, are heavy, and often consist of multiple individual components.

State of the Art

Optical metasurfaces have been developed as an alternative. They are classified as diffractive optical elements. Unlike conventional diffraction gratings, they utilize specially designed nanostructures (subwavelength meta-atoms). They are applied as nanostructured layers onto a substrate or directly carved out of it. Properties of light such as amplitude, phase, and polarization can be precisely controlled through the geometry and arrangement of the nanostructures. Today, in many areas, they achieve the performance of classical glass components or even surpass it in specialized applications.

Technology

Researchers in the Institute for Nanotechnology (INT) at KIT use state-of-the-art methods such as electron beam lithography for the customized fabrication of optical metasurfaces. First, calculations determine the phase that the light has to have at each position on the surface. Each point is translated into a specific nanostructure, which is then fabricated in materials such as silicon, titanium dioxide, or other transparent high-index materials. The focus at KIT is on beam shaping for the visible and infrared spectral ranges – including the formation of flat-top profiles (light beams with uniform brightness) in the UV, visible, and infrared ranges, as well as the formation of light lines and beam deflection.

Advantages

Optical metasurfaces are flat and much more compact than glass lenses. This enables the creation of ultra-thin lens systems. In certain applications, optical metasurfaces can replace multiple optical components with a single surface, thereby reducing weight, space requirements, and system complexity – making them ideal for mobile devices. Furthermore, they can be manufactured using the same CMOS-compatible processes as semiconductor chips, meaning that an industrial infrastructure for large-scale production already exists.

Options for Companies

As an opportunity for collaboration, KIT offers the development of small prototypes. Within KIT, metagrids with an edge length of up to 2 millimeters can be produced. In collaboration with additional external partners, it would be possible to manufacture metagrids with an edge length of up to 15 centimeters.