Double helix microfiber coupler enhances refractive index sensing based on Vernier effect

Abstract

A double helix microfiber coupler (DHMC) with minimum diameter of 3.4 µm has been fabricated and studied in this paper. The internal mechanism of the Vernier effect is analyzed theoretically and experimentally. The RI sensitivity of the sensor with Vernier effect is up to 27326.59 nm/RIU in the RI range of 1.3333–1.3394, which is nearly 6 times as that of the sensor without Vernier effect. The proposed microfiber structure which is simple to manufacture, and good robustness, has potential applications in many aspects such as high resolution chemical measurement and biomolecular detection.