Conventional round and curved lenses are the key element in refracting telescopes. While there have been advances in the materials used, the coatings, and the use of multiple lenses to correct distortions, basic lens design has not changed much since the time of Galileo.
Metalenses promise to revolutionize optics by replacing the bulky, curved lenses with a simple, flat surface.
A metalens takes a new approach to focusing light. Rather than exploiting the diffraction properties of glass, a metalens uses tiny pillars, typically made of titanium dioxide, to bend wavelengths toward the focal point.
The pillars are arranged in different patterns where each specific pattern focuses a different color of light. This short 2-minute video by Science Magazine does a good job of illustrating the concept in simple terms.
Recently, researchers from the Harvard School of Engineering have announced the development of the first single metalens that can focus almost the entire visible spectrum of light in the same spot. The Harvard metalens covers 470 nanometers (bold blue) to 680 nanometers (deep red) while a healthy eyeball reacts to wavelengths ranging from about 380 to about 700 nanometers. The Harvard metalens is a good prototype and additional advances may allow it to cover the whole visual spectrum.
A BC Company, NexOptic, has similar goals: to enable bigger apertures in small devices. They claimed to have developed a prototype telescope that was unveiled at the Macmillan Planetarium last year.
NexOptic has not revealed details on how their technology works but the prototype was evaluated on some moon images by a RASC-Calgary member, Larry McNish.
This is still early stage technology and a number of challenges remain for metalenses but hopefully it will enable dramatically smaller and lighter telescopes in the future.