Abstract
We developed chip-scale remote refractive index sensors based on Rhodamine 6G (R6G)-doped polymer micro-ring lasers. The chemical, temperature, and mechanical sturdiness of the fused-silica host guaranteed a flexible deployment of dye-doped polymers for refractive index sensing. The introduction of the dye as gain medium demonstrated the feasibility of remote sensing based on the free-space optics measurement setup. Compared to the R6G-doped TZ-001, the lasing behavior of R6G-doped SU-8 polymer micro-ring laser under an aqueous environment had a narrower spectrum linewidth, producing the minimum detectable refractive index change of 4 × 10-4 RIU. The maximum bulk refractive index sensitivity (BRIS) of 75 nm/RIU was obtained for SU-8 laser-based refractive index sensors. The economical, rapid, and simple realization of polymeric micro-scale whispering-gallery-mode (WGM) laser-based refractive index sensors will further expand pathways of static and dynamic remote environmental, chemical, biological, and bio-chemical sensing.
Highlights
We rely on the use of various sensors in our modern lives
We developed chip-scale remote refractive index sensors based on Rhodamine 6G (R6G)-doped polymer micro-ring lasers
The maximum bulk refractive index sensitivity (BRIS) of 75 nm/RIU was obtained for SU-8 laser-based refractive index sensors
Summary
We rely on the use of various sensors in our modern lives. This is more true than ever in the eminent internet-of-things (IoT) era, where massive deployment of sensors is anticipated. Silica based WGM resonators with diverse geometries, such as sphere [4], toroid [10, 11], ring [1], and disk [12] have been prominently investigated They are the possible candidates for the remote sensing of the environment by measuring the index change caused by various factors. Free-space measurement setups may make such passive-cavity based optical sensing feasible [21, 22]; lower signal intensity and polarization dependent directional scattering limits its applications in diverse geometrical resonators. In order to realize a simple, robust, and versatile platform for remote refractive index sensing, organic dye R6G-doped polymer SU-8 and TZ-001 micro-ring lasers were fabricated in sequence on the fused-silica wafer with patterned microring template. The sensitivities and detection limits of both polymer refractive index sensors were reported, respectively
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