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. 2022 Dec 9;8(49):eade7556. doi: 10.1126/sciadv.ade7556

Fig. 1. BIC-induced topological distribution of optical force for manipulation of nanoparticles.

Fig. 1.

(A) Schematic of a PhCS supporting BIC with topological optical force for trapping nanospheres in water. Holes in the PhCS can be twisted with a rotation angle of αtop for the top layer and αbot for the bottom layer. (B) Illustration of topological force for trapping and dispersing nanoparticles on two bands with BICs in untwisted PhCS. (C) Topological force for trapping nanoparticles with spinning pattern in twisted PhCS. Insets in (B) and (C) show the distributions of force vectors in momentum space. With the twisted PhCS, nanoparticles will be trapped to or repelled from the center in a spinning feature like a swirl, which is different from the untwisted case leading to a rectilinear motion. (D) Iso-frequency surface and color-mapped quality factor of the untwisted PhCS for two eigenmodes (αtop = αbot = 0°). Corresponding distribution of far-field polarization states of (E) the upper band (top) and (F) the lower band (bottom) in (D). (G) Iso-frequency surface and color-mapped quality factor of the twisted PhCS with αtop = 25°, αbot = 0° for two eigenmodes. Elliptical polarization states induced by the twist PhCS for (H) the upper band (top) and (I) the lower band (bottom) in (G).