Designing a terahertz optical sensor based on helically twisted photonic crystal fiber for toxic gas sensing.

A novel helically twisted photonic crystal fiber (PCF) is designed and proposed for sensing toxic gases with refractive indices ranging from 1.00 to 1.08.

High-performance surface plasmon resonance fiber sensor based on cylindrical vector modes.

Cylindrical vector modes with azimuthal polarization and low transmission loss are proposed for the first time to be utilized in a novel design of a surface plasmon resonance (SPR) sensor based on a circular photonic crystal fiber (C-PCF). A C-PCF with a ring of air holes in the cladding is designed where a gold layer with a thickness of 44 nm is coated on the outer cladding surface. The optimal geometric parameters are determined using the finite-element method (FEM) for a high-quality TE mode and high sensitivity of the sensor.