A high sensitivity refractometer based on a partial liquid-filled hollow-core photonic bandgap fiber

A novel and high sensitivity refractometer is realized by using a short partial liquid-filled hollow-core photonic bandgap fiber (HC-PBGF). Since the liquid filled into partial air-holes of HC-PBGF forms an asymmetric waveguide structure, the confinement loss of the partial filled HC-PBGF is high sensitive to the refractive index of the filled liquid when the wavelength of the input light on Y polarization mode is fixed at the band gap edge. The proposed refractometer can realize a trace measurement by filling the tested liquid into HC-PBGF partially with 1 mm length and the refractive index sensitivity in theory is as high as 1.5×10
⁻⁸
at approximately 1.333.