Novel dual beam fiber traps using endlessly single-mode photonic crystal fiber

The dual beam fiber trap is an important tool in the field of optical micromanipulation. The characteristics of these traps are governed by the fibers used. Photonic crystal fibers have emerged in recent years and may be engineered to have vastly different properties to conventional fibers. In particular, endlessly single-mode photonic crystal fiber (ESM-PCF) will guide any wavelength of light in a single-mode and is commercially available in core diameters up to 35 μm. By utilising these unique properties, we show that it is possible to create novel dual beam ESM-PCF traps for micron size particles. Firstly, we characterise an ESM-PCF trap when using a near-infrared laser coupled into a 25 μm core fiber when trapping a sample in a square capillary. We calculate the trap stiffness for polymer micro-spheres and show that aside from the expected confining potential, it is possible to create line and repulsive potentials. Interference effects due to the capillary are observed. Secondly, we create a dual wavelength standing wave trap which can selectively move two sizes of particles in an optical conveyor belt. Finally, we use a supercontinuum source to create the first white light dual beam fiber trap and show that the low coherence length of the source results in interference free potentials. Overall PCF has great promise for future studies.