Methods and devices for optical sorting of microspheres based on their resonant optical properties

摘要

Microspheres are sorted by resonant light pressure effects. An evanescent optical field is generated when light is confined within the interior of an optical element such as a surface waveguide, a tapered microfiber, or a prism. Microspheres brought within vicinity of the surface are subjected to forces that result from a coupling of the evanescent field to whispering gallery modes (WGM) in the microspheres. Alternatively, a focused laser beam is directed close to the edge of the microspheres to exert resonant optical forces on microspheres. Optical forces are resonantly enhanced when light frequencies match WGM frequencies in the microspheres. Those microspheres for which resonance is obtained are more affected by the evanescent field than microspheres for which resonance does not occur. Greater forces are applied to resonating microspheres, which are separated from a heterogeneous mixture according to size.

主权项

1. A method of separating and collecting microspheres comprising:
propagating light within an interior of an optical element at a surface of the optical element, thereby generating an evanescent field exterior to the optical element in a vicinity of the surface; providing a heterogeneous mixture of microspheres in the vicinity of the surface within the evanescent field, each microsphere having a size and a refractive index, thereby applying forces on at least some of the microspheres by the evanescent field according to size and refractive index; permitting movement of at least some of the microspheres upon which forces are applied by the evanescent field, thereby separating at least some of the microspheres of the heterogeneous mixture from a remainder of the mixture according to at least one of size and refractive index; and collecting at least one of: the separated microspheres; and the remainder of the mixture; wherein providing a heterogeneous mixture of microspheres comprises providing free falling microspheres.