Figure 7

Optical confinement of absorbing particles using light capsules with different darkness inside.

(a–c) Trapping demonstration using light capsule with σ = 1.5. Such bottle beam has very weak force on the particle. When we shifted the particle a little away from the center, it itsself moved slowly back to the center. (d) But with a little external force exerted by the flowing fluid, it easily escaped from the optical bottle. (e–h) The demonstration of stably trapping and manipulating a magnetic particle using bottle beam with σ = 2.5. The particle could be confined within the capsule even with larger external force. (i–l) Enhanced confinement and manipulation of a magnetic particle employing the first-order bottle beam (m = 0, l = 1, σ = 2.5). Compared with the previous trapping, the trapped particle has smaller motion range indicated by the dashed circles under a certain moving speed of the fluid. The arrows respresent the directions of the flowing fluid.