A team of researchers from NASA’s Jet Propulsion Laboratory and CalTech have developed a range of ultra-thin, optical components capable of arbitrary manipulation of light. The devices, dubbedmetasurfaces, are able to locally modify the properties of a light-field in ways difficult to achieve with standard optics.
So what does it mean to manipulate light? Light, an electromagnetic field that propagates through space, can be completely described at one wavelength by polarization, phase, andamplitude. If we know what the light-field looks like now, we can accurately predict what it will look like in the future by knowing only these properties.
Any optical component that exists can be thought of as essentially modifying one or more of the above properties. For example, in free-space optical systems, polarization is modified using wave retarders, polarizers, and polarization beam-splitters; phase is shaped using lenses, curved mirrors, or spatial phase modulators; and amplitude is controlled via neutral-density absorptive or reflective filters. Therefore, by combining many components, we’re able to build systems that can manipulate the light-field to varying degrees.
However, as you may have guessed, in order for us to have full control, we normally need many components, each of which is usually bulky and expensive. Think of the optics in a telescope or DSLR for example.
What is a metasurface?
Metasurfaces are planar (~2D) structures that locally modify the polarization, phase, and amplitude of light in reflection or transmission, where each sub-pixel is smaller than the wavelength of light. When we say 2D, the vertical dimension is normally <100nm, or ~1,000x smaller than a human hair. Therefore, these flat, highly functional optical components can be manufactured in exactly the same way as state-of-the-art electronics, such as microchips, which use high resolution lithographic techniques.