Rib waveguides for trapping and transport of particles

Abstract

Rib waveguides are investigated as an alternative to strip waveguides for planar trapping and transport of microparticles. Microparticles are successfully propelled along the surface of rib waveguides and trapped in the gap between opposing rib waveguides. The trapping capabilities of waveguide end facets formed by a single and opposing waveguide geometries are investigated. The slab beneath a rib waveguide continues to guide light after the end facet of a rib waveguide. Thus particles can be trapped in wider gaps formed by opposing rib waveguides than with strip waveguides. Rib waveguides were found more efficient in trapping a collection of particles in the gap and particles could be moved to different locations in the gap by changing the relative power in the two opposing rib waveguides. Numerical simulations are used to show that the trapping efficiency on the surface of rib and strip waveguides is comparable. The simulations also confirm the advantage of opposing rib waveguides for trapping particles in wide gaps. The low sidewalls of rib waveguides give low propagation losses and make it easy to integrate rib waveguides with other functions in a lab-on-a-chip where particle trapping and transport is required.

Perspective on light-induced transport of particles: from optical forces to phoretic motion

“…(a) An evanescent wave generated by total internal reflection from an interface between media with a sufficient contrast of refractive indices propagates in an optically less dense medium and propels the particle over the illuminated area [8,367]. The distance over which the particle can be transported can be significantly increased by fabricating a channeled waveguide on top of the substrate (blue) in the form of (b) a strip [239,364,369], (c) a rib [370], or (d) a buried waveguide [359,371,372]. (e) Instead of a planar dielectric structure, a more complex nanostructure can be manufactured on top of the substrate, in which a mode is formed inside a slot waveguide and used to localize and guide the particles within the slot [368,373].…”

Quantitative phase microscopy of red blood cells during planar trapping and propulsion

“…Both strip and rib waveguides have been used in the past for optical trapping applications. 22 , 24 ESI † Fig. S4 and S5 show the phase map of RBCs placed on top of rib and strip waveguides with varying widths.…”

“…cells, bacteria and viruses) on the top of waveguide surfaces. 19 – 24 In contrast to the focused beam of traditional optical tweezers, WT works using an evanescent light field, which is generated from totally-internally reflected (TIR) light guided through a path of high refractive index contrast on a semiconductor chip. Trapping occurs due to the exponential decay of the evanescent field relative to the waveguide surface, which generates a vertical gradient force ( F x ) that pulls a refractive objective ( e.g.…”

Chip-based nanoscopy: towards integration and high-throughput imaging

“…Waveguide structures are today commonly employed in e.g. sensing applications 17 , Raman spectroscopy 18 and optical trapping 19,20 . Integrated photonic circuit enables easy beam shaping, and is well suited for integration with e.g.…”

“…Additionally, the photonic chips allow easy integration with other integrated optical functions such as e.g. optical trapping 19,20 and Raman spectroscopy 21 . Finally, the waveguide chips can be made cost-effective by mass-production.…”