In recent years, photonic biosensors have attracted increasing attention due to the enormous range of applications in many fields to which they may be put, including medical diagnostics, environment monitoring, organic chemical detection, temperature sensing, and work with magnetic fields. In this work, photonic crystal fibre (PCF) was utilised as a biosensor using a Finite Element Method (FEM). Several important optical sensor properties such as the field distribution profiles, the real part of the effective refractive index and the relative sensitivity of the proposed PCF structure are affected by mode coupling between the fundamental mode and the second order super mode of the inner and outer cores, respectively. These properties were thus those studied by applying FEM. The proposed biosensor can thus be used for bio-sensing, as the holes in the PCF are filled with analytes. Relatively high sensitivity can thus be obtained using appropriate design by selecting design parameters such as the radius of holes in the cladding region and pitch distance, or distance between the centres of neighbouring holes, appropriately. The results from this work show that the electric field distribution is affected by mode coupling between the outer and inner modes; the effects of mode coupling of the PCF on the relative sensitivity were also determined.

Based on heat accumulation effects, symmetric optical waveguides in glass can be obtained via femtosecond laser irradiation. Such modification inside glass is interesting in terms of developing integrated mini-optical devices with 3-D structures and micro channels for biosensors. This work experimentally investigated the formation of micro-channels inside porous glass irradiated with an 800 nm, 100 fs, and 250 kHz femtosecond laser with scanning speeds ranging from 250 μm/s to 1000 μm/s at a fixed power of 300 mW. Strong heat accumulation effects were thus observed at laser scanning at 250μm/s, which offered significant variations in structure morphology.