Design and simulation of liquid infiltrated photonic crystal fibre in terahertz frequencies

Ethanol, methanol and water are polar solvents with similar physical properties albeit contrasting chemical properties. Therefore, it is essential to provide accurate and reliable methods for detecting these liquids. In this paper, a novel liquid infiltrated photonic crystal fibre for ethanol, methanol and water sensing is introduced. The novel structure is modelled, simulated and analysed in the terahertz (THz) region using a full vectorial finite element method. It is shown that the THz light, which is guided using modified total internal reflection, is confined within the infiltrated analytes with negligible losses. For the detection of infiltrated liquids at 1.6 THz operating frequency, the proposed fibre demonstrates high sensitivities up to 99.73% and confinement losses in the order of 10−4 dB/m. Manufacturing of the proposed fibre is feasible using existing fabrication technologies and it is envisaged that the fibre may provide a solution to existing challenges in detecting common polar solvents.