Diffractive solar sail

[1][2] Current diffractive sail designs use thin metamaterial films, containing micrometer-size gratings based on polarization or subwavelength refractive structures, causing light to spread out (i.e. diffract) and thereby exert radiation pressure when it passes through them.

[2][3] The idea of using diffraction for a solar sail was first proposed in 2017 by researchers at the Rochester Institute of Technology.

[4] This was enabled in part by advances in material design and fabrication (particularly of gratings), and optoelectronic control.

[1][2][6] In 2022 the NIAC project reached phase III and gained US$2 million of support from NASA, with involvement of researchers from both Johns Hopkins University and the Rochester Institute of Technology.

[5] Photons can be reused: either by passing through a second diffraction grating for more thrust, or by going to a solar cell to provide electricity.