Selective infiltration of photonic crystal fibres for waveguide arrays

Abstract

Photonic crystal fibres (PCFs) can be used as a platform for the study of periodic photonic structures as well as the novel linear and nonlinear physical effects associated with them. The cladding holes in these micro-structured fibres can be infiltrated with a liquid utilising capillary action. This can be prevented in selected holes through the prior blocking of one end, producing periodic photonic arrays in the shape of the infiltration, providing a customised array shape within a low defect, high quality PCF. The coupling pattern of guided light in an input hole re- distributing to neighbouring infiltrated holes can be modified through thermo-optic relationships, which, together with non-linear effects resulting from high light intensity, enables the study of novel physical phenomena of both periodicity and non-linearity. We developed a blocking procedure which, when applied to hexagonal ring Large Mode Area (LMA) PCFs, allowed a single row of holes to be infiltrated by an index matching oil with a well-defined thermal-optic relationship. With laser light guided into a single infiltrated hole and the sample maintained at 55±0.1°C, a linear discrete diffraction pattern was observed in the output intensity distribution, indicative of a one dimensional periodic photonic array. The investigation of non-linear self trapping at a constant temperature produced results obscured by asymmetric linear coupling. Proposed alterations to the blocking procedure could allow for the formation of more complex infiltration patterns with novel coupling relationships and non-linear effects. Further development can lead to applications in bio-sensing and beam manipulation.