Figure 2: Experimental set-up and materials.
From: Helicity-dependent three-dimensional optical trapping of chiral microparticles
The set-up consists of two counterpropagating moderately focused non-vortex or vortex beams with identical divergence angle, wavelength, helicity and power. D is the distance between the two focal planes where beam waist radius is w0. (a) Optical trapping of a transparent spherical chiral liquid crystal droplet of radius R at the origin (x, y, z)=(0, 0, 0) is considered in all cases, see upper and lower panels. (b–d) Experimental bell- and doughnut-shaped transverse intensity distributions are shown in panels b and c, whereas their azimuth-averaged radial profiles (thick grey lines in panel d) are described by the fundamental and the first-order Laguerre–Gaussian profiles (thin solid lines in panel d). (e) Sketch of a radial cholesteric droplet. Concentric circles illustrate the onion-like arrangement of the supramolecular pseudo-layers of thickness p/2 where p is the helical pitch. (f,g) Full transmission images of a droplet under left/right-handed circularly polarized illumination (LHCP/RHCP) are shown.
