Highly sensitive refractometer with photonic crystal fiber long-period grating

TL;DR

This paper introduces a highly sensitive refractometer using a photonic crystal fiber long-period grating, achieving record sensitivity and minimal detectable index change through sample infiltration into the fiber holes.

Contribution

The paper demonstrates the first use of a large mode area photonic crystal fiber long-period grating for highly sensitive refractometry with record sensitivity.

Findings

Maximum sensitivity of 1500 nm/RIU at RI 1.33

Minimal detectable index change of 2×10⁻⁵

Record-high sensitivity for fiber gratings

Abstract

We present highly sensitive refractometers based on a long-period grating in a large mode area PCF. The maximum sensitivity is 1500 nm/RIU at a refractive index of 1.33, the highest reported for any fiber grating. The minimal detectable index change is $2\times 10^{-5}$. The high sensitivity is obtained by infiltrating the sample into the holes of the photonic crystal fiber to give a strong interaction between the sample and the probing field.