Optical Trapping with Focused Surface Waves

• Published in: Annalen der Physik Vol. 532; no. 4
• Main Authors: Xiang, Yifeng, Tang, Xi, Min, Changjun, Rui, Guanghao, Kuai, Yan, Lu, Fengya, Wang, Pei, Ming, Hai, Zhan, Qiwen, Yuan, Xiaocong, Lakowicz, Joseph R., Zhang, Douguo
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.04.2020
• Subjects: Beads; Electric fields; Electromagnetic absorption; Evanescent waves; Gold; Optical microscopes; Optical trapping; optothermal effects; Polystyrene resins; surface plasmons; Surface waves; thermal convection
• ISSN: 0003-3804; 1521-3889
• DOI: 10.1002/andp.201900497

Near‐field optical trapping can be realized with focused evanescent waves that are excited at the water–glass interface due to the total internal reflection, or with focused plasmonic waves excited on the water–gold interface. Herein, the performance of these two kinds of near‐field optical trapping techniques is compared using the same optical microscope configuration. Experimental results show that only a single‐micron polystyrene bead can be trapped by the focused evanescent waves, whereas many beads are simultaneously attracted to the center of the excited region by focused plasmonic waves. This difference in trapping behavior is analyzed from the electric field intensity distributions of these two kinds of focused surface waves and the difference in trapping behavior is attributed to photothermal effects due to the light absorption by the gold film. Two kinds of surface waves are excited and focused to trap dielectric microbeads in liquid. The focused evanescent waves trap a single bead near the focused center, whereas the focused plasmonic waves trap many beads from a large trapping region. Accumulation and ordering of beads in the focused plasmonic field is due to the generation of thermal convection.