Polyvinyl alcohol coating microbottle resonator on whispering gallery modes for ethanol liquid sensor

•This research explored coated microbottle resonator (MBR) as an ethanol sensor.•The MBR-PVAs formed three different sizes with Q-factor >104.•The ethanol concentrations used are from 10% ppm to 100% ppm.•Sensitivity, linearity, stability and repeatability results analysis used to determined MBR-PVAs performance.•The stability testing for 60 min showed that MBR-PVAs suitable as an ethanol sensor.•The enormous size MBR-PVA-C marked the best performance of all. This experimental paper study on the effect of polyvinyl alcohol (PVA) coating on whispering gallery modes on microbottle resonator (MBR) as liquid ethanol sensor. The silica fiber SMF-28 is used to create microbottle resonator using a technique known as “soften-and-compress” and formed in three sizes with bottle length Lb, stem diameter of Ds and bottle diameter of Db. The MBR then coated with PVA using a drop-casting technique with the coating diameter 104 for Q-factor for all condition with MBR-PVA-C is the highest, 2.783 × 104. The ethanol liquid with concentrations ranging from 10% to 100 %ppm is used for sensing purposes. Sensitivity, linearity, repeatability and stability performance by MBR-PVAs then compared between transmitted spectral and wavelength shift analysis. The MBR-PVA-C defined to have the best performance for all than another size of MBR-PVAs. Transmitted spectral analysis showed the sensitivity is 0.2699 dB/%ppm with 99.2% of linearity, and wavelength shift analysis showed the sensitivity is 0.2 pm/%ppm with a linearity of 98.01% respectability. Hence, MBR-PVAs experienced three cycles of repeatability and a 60-second stability procedure for performance optimization.