Figure 3.

Analysis of the Brownian motion and thermophoretic energy of a 22-nm polymer particle trapped on PhC resonators and the temperature profile around the resonators. The laser power coupled into the silicon nitride PhC resonator was ~11 mW. The images used for the particle tracking were taken with an exposure time of 30 ms. For (a) and (b) the particle was tracked for ~8 seconds. (a, b) Histograms of the displacement of the trapped particle from the trap center in the X and Y direction. The direction of the laser is the positive Y direction. (c) The Y-position of the trapped 22-nm particle shown in Figure 2a-e (Supplementary Movies 1, 2). The positions were measured relative to the position of the particle at the beginning of Supplementary Movie 1. (d) Temperature profile as numerically calculated under the experimental conditions. The maximum temperature increase is 0.3 K at mid resonator height. (e) Line plots of the temperature increase at mid resonator height in the X direction at y = 0 for the silicon nitride device operating at 1064 nm (same as the device shown in (d)) and a similar silicon device operating at 1550 nm²⁴. Solid line: silicon nitride device; dashed line: silicon device. The power coupled into the cavity was assumed to be 6 mW in both simulations. The arrow represents the direction of the flow. (f) Calculation of the thermophoretic free energy of a 22-nm polymer particle under our experimental conditions for the silicon nitride device operating at 1064 nm and the silicon device operating at 1550 nm²⁴. Solid line: silicon nitride device; dashed line: silicon device. The free energy was deduced from the concentration profile calculated numerically. Scale bar in (d), 5 μm.