Towards practical liquid and gas sensing with photonic crystal fibres: side access to the fibre microstructure and single-mode liquid-core fibre

Abstract

Photonic crystal fibres (PCFs) have important applications in sensing the optical properties of fluids. To this end, the material should be inserted into the fibre holes in order to interact with the propagating field. When dealing with liquids, it is particularly interesting to exclusively insert the sample into the core of a hollow-core PCF, which then guides light through the liquid via total internal reflection. Nevertheless, there is still a series of issues to be addressed before fluid sensing with PCFs becomes practical. The work described here proposes and demonstrates possible solutions for two of these issues: (a) how to insert the sample through a lateral access to the fibre longitudinal holes so that the fibre tips are free for optical handling and accessing and (b) in the case of a liquid-core PCF, how to reduce the number of propagating modes.