Diffractive lightsails use small gratings embedded in thin films to produce diffraction (which causes light to spread out when it passes through a narrow opening).
Diffractive light sails are a potential advance on traditional reflective light sails. They can redirect light (and therefore thrust) without attitude changes. They are “aimed” using optoelectronic control rather than mechanical control, so they remain square to the incident sunlight. Thus they maintain their full capture area without angling to redirect light.
Because all light is transmitted, heating issues are less than reflective sails and the transmitted photons can still be used for PV panels.
They have been proposed for a solar polar orbit (high ecliptic inclination), which are challenging to accomplish with chemical rocket propulsion.
The Diffractive Solar Sailing project was selected for Phase III study under the NASA Innovative Advanced Concepts (NIAC) program.
Wikipedia on diffractive solar sails: https://en.wikipedia.org/wiki/Diffractive_solar_sail
Circumnavigating the sun with diffractive solar sails: https://www.sciencedirect.com/science/article/pii/S0094576521003337
Are there plans for a demonstration mission?