Nanophotonics is a branch of optical engineering that uses nanoscale structures to control photons. The ability to control photons opens up new possibilities in quantum chips, sensors, lenses, and holograms for the AR/VR world.
One way that photons can be manipulated is by using a metasurface. A metasurface starts off as a silicon dioxide wafer. Using lithography techniques from the semiconductor industry, a pattern is “printed” on the wafer. Most of the time, the pattern is of free standing pillars. Each pillar angles the outgoing photon (remember photons are both particles and waves) according to Snell’s law. For example, in the image below, red light is being focused by the wafer in the plastic container. By changing the distance between the light source and the wafer, blue and green wavelengths can be focused as well. The goal is to replace bulky lenses with an object like this that is as thin as a piece of hair, yet has the ability to focus light.