Fig. 3: Experimental details.
From: Evanescent field trapping and propulsion of Janus particles along optical nanofibers
a Schematic of the optical setup (not to scale). A single-mode ONF is immersed in a water suspension of 3 μm silica and Janus particles which are selectively trapped and delivered to the ONF waist by low-power (1.3−1.7 mW) optical tweezers. Laser beams 1 and 2 produce counterpropagating modes polarized in xz- or yz-planes, corresponding to H or V polarization states of the beams. To ensure the polarization is maintained upon propagation to the ONF waist, we use adjustable compensators, PC1 and PC2, consisting of two quarter-wave plates each. The ONF and the particles are imaged by a CMOS video camera through the trapping objective under white-light illumination in Köhler configuration; PBS is a polarizing beamsplitter. b Particles are seen trapped in the polarization plane. JPs with 10- and 20-nm-thick coating were studied in two different samples, both ONFs having Rf = 0.35 μm as measured by SEM; the transmitted optical power through the fiber was 50 mW. c, d Measured (markers with error bars respectively indicating the mean values and 50% standard deviation ranges obtained for 3-5 different JPs) and simulated (markers connected via a spline interpolation) stable orientations of JPs vs. the gold thickness and the optical power transmitted through the ONF. Insets: particle images with enhanced lightness and contrast.
