Optical nanomanipulation and structured-beam optical traps

In this article, we discuss the basic principles of optical manipulation of nanoparticles to micron sized dielectric particles. We first discuss far-field optical manipulation of single molecules, deoxyribonucleic acid (DNA), quantum dots, nanowires to particles exhibiting nonlinear Kerr effects. Apart from optical trapping from a single optical focus, structured beam consisting of multiple foci as well as doughnut-beam optical traps can be used to match specific optical properties of the particles. Applying structured beam far-field optical trapping enables simultaneous transfer of linear and orbital angular momentum. For optical manipulation in the near-field regime, we briefly discuss its origins via evanescent waves on surfaces and metallic tips that are smaller than the diffraction limit. This has led to the study the interaction of nanoparticles on metallic surfaces excited at resonant conditions to induce surface plasmons. Finally, we discuss the future outlook by drawing on some recent works in optical manipulation within a living animal and extrapolating potential experiments in biomolecular nanomanipulation and stimulation to resolve challenging neurobiology questions.