Fig. 2: Refractive and diffractive optics for light manipulation.

a Focusing optics (left: refractive optics, right: difractive optics) of incoming light source at different wavelengths. b Schematic of an ultra-thin multi-level micro-optics for focusing light. (insert top right) Thickness profiles for multi-level optics. (insert bottom right) A conceptual diagram of transferred diffractive micro-optics onto a flexible/stretchable substrate. c A conformal layer of diffractive optics directly attached to the surface of a conventional refractive lens. a Adapted with permission from ref. ³⁸, Springer Nature. b Adapted with permission from ref. ⁸, Elsevier. c Adapted with permission from ref. ⁸, Elsevier, adapted with permission from ref. ¹³⁹, IOP publisher