Abstract

Hollow-core photonic crystal fibre (HC-PCF) uniquely allows low-loss propagation of light in a microscale channel, where it can strongly interact with infiltrated liquids, gases, and particles. For instance: HC-PCF waveguide modes provide well-defined optical forces that can be used to launch and propel microparticles and biological cells over long distances [1,2]. Particle dynamics can be monitored by in-fibre Doppler velocimetry, offering a unique way to study viscous forces in microfluidic channels. Experiments in air-filled HC-PCF uncovered a novel optothermal trapping mechanism [3], with potential applications in lab-on-a-chip devices. Furthermore, exciting a coherent superposition of higher-order waveguide modes can create a mode-based “optical conveyor” that combines long-range transport with a positional accuracy of about 1 μm [4].

‘Flying particles’ in HC-PCF can also be used as reconfigurable microscale sensors [5]. For example, a measurement of the transverse displacement of a charged microparticle can be used to map the electric field pattern near the surface of a multi-element electrode with a spatial resolution of ~100 μm.

References 1. T. G. Euser et al., Opt. Lett. 34, pp. 3674-3676 (2009). 2. O. A. Schmidt et al., Opt. Lett. 37, pp. 91-93 (2012). 3. O. A. Schmidt et al., Phys. Rev. Lett. 109, 024502 (2012). 4. O. A. Schmidt et al., Opt. Express 21, pp. 29383-29391 (2013). 5. D. Bykov. et al., Nat. Phot. 9, pp. 461–465 (2015).