Fabrication

Materials science

Refractive index

Polarimetry

Infrared

Scattering

Achromatic lens

Perovskite (structure)

Photonic crystal

Physical chemistry

Polarization (electrochemistry)

Photonics

Alternative medicine

Laser

Physics

Nanotechnology

Waveplate

Optics

Iridescence

Nanocrystal

Crystallography

Medicine

Chemistry

Birefringence

Optoelectronics

Pathology

Nature Photonics

Waveplates are widely used in photonics to control the polarization of light1,2. Often, they are fabricated from birefringent crystals that have different refractive indices along and normal to the crystal axis. Similar optical components are found in the natural world, including the eyes of mantis shrimp3,4 and the iridescence of giant clams5, fish6 and plants7. Optical retardation in biology relies on sophisticated self-assembly, whereas man-made systems comprise multiple-layered materials8–11. Here we report a discovery that bridges these two design principles. We observe wideband achromatic retardation in the visible and near-infrared (532–800 nm) regions for Cs4PbBr6 perovskite crystals embedded with CsPbBr3 nanocrystals. We explain our observations as matched dispersions of the refractive indices of the ordinary and extraordinary rays caused by the ordered embedding of the nanocrystals in the host. The wideband performance and ease of fabrication of these perovskite materials are attractive for future applications. Perovskite crystals of Cs4PbBr6 embedded with CsPbBr3 nanocrystals are shown to act as wideband, achromatic waveplates in the visible and near-infrared regions.

Solution-processed inorganic perovskite crystals as achromatic quarter-wave plates