Fig. 4: Chiral selective retroreflection of CSRs.
a Schematic illustration of the omnidirectional selective retroreflection (white light in, blue light out, regardless of incoming light direction) due to the radial helix arrangement in a CSR shell with blue λ0. Pink arrows represent the local helix orientation m, white circles represent the director orientation (continuous: n in image plane; dotted: n perpendicular to image plane). b Illustration of polarization-based image subtraction, using reflection polarizing microscopy photos of a cluster of CSRs with green retroreflection. Scale bars: 100 µm
