Effect of PMMA and PVA coating on the performance of optical microbottle resonator humidity sensors

Abstract

This article compares the performances of uncoated and coated optical microbottle resonators (MBR) for humidity sensing. A technique called “soften‐and‐compress” was used to form the MBR with midriff diameter of D b = 190 μm, stem diameter of D s = 125 μm and bottle length of L b = 182 μm. The MBRs were prepared in three different conditions, which are noncoated MBR, PMMA (poly methyl meth acrylate) coated MBR, and PVA (polyvinyl‐alcohol) coated MBR. The MBRs characteristic was investigated by employing a 2 μm tapered microfiber and tested for humidity sensing within a humidity range of 40% to 95%. The Q‐factor obtained were >104 for all MBRs. The performance as humidity sensor was defined by the sensitivity and linearity of MBRs, which were investigated based on wavelength shift and also the transmitted power. The MBRs are undergoing a 180‐seconds stability test at 65% RH humidity level. It is found that the PVA coated MBR performed better than other MBRs as a humidity sensor based on sensitivity, linearity, and stability measurements.

High-sensitivity balloon-like thermometric sensor based on bent single-mode fiber

“…To investigate the effect of the PVA coating on the sensitivity of the bent structure, the bent fiber was coated with The occurrence of the blue-shift of the proposed sensor might be attributed to the higher refractive indices of the resonance coating material, as well the refractive indices of both the cladding and core of the SMF being reduced due to the negative TOC, which is about −10 −4 [21,24,25]. The PVA-coated balloon structure was shown to have the highest sensitivity due to its tunable refractive index [26].…”

Review of Optical Humidity Sensors

“…A shift in the resonance wavelength is governed by the humidity-induced changes in the average interparticle separation. The response time was reported to be 200 ms. Md Ashadi Md Johari et al [ 162 ] sensitized microbubble resonators with PVA or poly methyl meth acrylate (PMMA) coatings to absorb moisture and change the effective index seen by the resonant modes. A 2 μm diameter optical microfiber was used to couple light in and out of the microresonator.…”