Particle propulsion in hollow-core photonic crystal fibre

This talk reviews our recent work on optical trapping and propulsion of microparticles in hollow-core photonic crystal fibre (HC-PCF). HC-PCF uniquely allows low-loss propagation of light in a microscale channel. The resulting well-defined optical forces can be used to launch and propel microparticles [1] and biological cells [2] over long distances. The particle dynamics are monitored by using an in-fibre Doppler velocimetry technique [3], offering a unique way to study viscous forces in microfluidic channels. Recent particle propulsion experiments in air-filled HC-PCF [4] have led to the discovery of a novel optothermal trapping mechanism [5], which has potential applications in lab-on-a-chip devices. Recently, we have shown that a coherent superposition of co-propagating higher-order waveguide modes can create a mode-based "optical conveyor belt" that combines long-range transport with a positional accuracy of about 1 μm [6]. Finally, we demonstrate a new type of "flying particle" sensor which maps the electric field strength along a HC-PCF by measuring the transverse displacement of an optically propelled charged microparticle [7]. This unique sensor allows electric field to be mapped with very high positional accuracy over long distances and is suitable for otherwise inaccessible or harsh environments.

References
[1] T. G. Euser et al., "Precise balancing of viscous and radiation forces on a particle in liquid-filled photonic-bandgap fiber," Opt. Lett. 34, 3674 (2009).
[2] S. Unterkofler et al., "Long-distance laser propulsion and deformation-monitoring of cells in optofluidic photonic crystal fiber," J. Biophotonics 6, 743–752 (2013).
[3] M. K. Garbos et al., "Doppler velocimetry on microparticles trapped and propelled by laser light in liquid-filled photonic crystal fiber," Opt. Lett. 36, 2020 (2011).
[4] O. A. Schmidt et al., "Metrology of laser-guided particles in air-filled hollow-core photonic crystal fiber," Opt. Lett. 37, 91 (2012).
[5] O. A. Schmidt et al., "Reconfigurable optothermal microparticle trap in air-filled hollow-core photonic crystal fiber," Phys. Rev. Lett. 109, 024502 (2012).
[6] O. A. Schmidt et al., "Mode-based microparticle conveyor belt in air-filled hollow-core photonic crystal fiber," Opt. Express 21, 29383-29391 (2013).
[7] D. S. Bykov et al., "Electric field sensing with high spatial resolution via a charged "flying particle" optically guided inside hollow-core PCF, " presented at OFS 23, best student paper award (2014).