Figure 2: Chiral microresonators.

(a) Calculated reflection, R⁺, from an L-chiral layer with pitch, p, and variable thickness, d (equation 4). A reflectance close to 100% (R⁺≈1) is obtained for a layer thickness larger than ≈5p. (b) Measured transmission spectrum of a 20 μm-thick polymerized CLC film between two glass substrates with planar texture for linearly polarized light. The photonic band gap is centred at ≈815 nm and has a width of ≈72 nm. The dashed lines falling within the stop band are the trapping wavelengths used in the optical trapping experiments. (c) Sketch of a polymeric particle with spherulite-like (radial) configuration of the helical structure. (d) Optical microscope image of the particle between crossed polarizers: the light and dark concentric shells are due to the spatial variation of the refractive index due to the chiral structure in the radial direction. (e) Scanning electron microscope image of a half particle showing the ‘onion-like’ structure.