Quantitative broadband chemical sensing in air-suspended solid-core fibers

TL;DR

This paper presents a novel broadband fiber sensor using air-suspended solid-core photonic crystal fibers for highly sensitive chemical detection, demonstrating excellent agreement with theoretical models and potential for significant sensitivity improvements.

Contribution

It introduces a new fiber sensor design with tunable properties and validates its effectiveness for broadband chemical sensing in liquids and gases.

Findings

Mode profiles match finite element calculations

Zero dispersion wavelength can be tuned via core diameter

Sensitivity can be increased by three orders of magnitude

Abstract

We demonstrate a quantitative broadband fiber sensor, based on evanescent field sensing in the cladding holes of an air-suspended solid-core photonic crystal fiber. We discuss the fabrication process, together with the structural- and optical characterization of a range of different fibers. Measured mode profiles are in good agreement with finite element method calculations made without free parameters. The fraction of the light in the hollow cladding can be tuned via the core diameter of the fiber. Dispersion measurements are in excellent agreement with theory and demonstrate tuning of the zero dispersion wavelength via the core diameter. Optimum design parameters for absorption sensors are discussed using a general parameter diagram. From our analysis, we estimate that a sensitivity increase of three orders of magnitude is feasible compared to standard cuvette measurements. Our study applies to both liquid and gas fiber sensors. We demonstrate the applicability of our results to liquid chemical sensing by measuring the broad absorption peak of an aqueous nickel chloride solution. We find striking agreement with the reference spectrum measured in a standard cuvette, even though the sample volume has decreased by three orders of magnitude. Our results demonstrate that air-suspended solid-core PCFs can be used in quantitative broadband chemical sensing measurements.