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

Since ethanol, methanol, and water are polar solvents with similar physical properties albeit contrasting chemical properties, it is essential to have a method of accurately and reliably detecting and differentiating the liquids. In this paper, a unique-structured liquid infiltrated photonic crystal fibre (PCF) for sensing ethanol, methanol and water, has been introduced. The structure has been modelled, simulated and analysed in the terahertz (THz) region using the full vectorial finite element method. It has been shown that the THz light, which is guided using modified total internal reflection (M-TIR), is confined within the infiltrated analytes with negligible losses. For the detection of infiltrated liquids at 1.6 THz operating frequency, the proposed PCF shows sensitivity levels above 99% and effective material losses (EMLs) in the order of 10(-4) dB m(-1). Manufacturing of the proposed fibre has been shown to be feasible using the existing PCF fabrication technologies. It is envisaged that the proposed PCF will provide a solution to the existing challenges in detecting common polar solvents.

Automated summary

This study introduces a unique-structured liquid infiltrated photonic crystal fibre for detecting ethanol, methanol and water. It is found that the proposed fibre can accurately and reliably detect and differentiate these liquids in the terahertz region, with high sensitivity and low losses.