Introduction of Microbottle Resonator for Honey Concentration Sensing

This paper investigates the behaviour of whispering gallery modes (WGMs) in a silica-based micro bottle resonator (MBR) for honey concentration sensing. The MBR was fabricated using the soften-and-compress technique on standard SMF-28 silica fibre, creating a bottle-shaped structure with controlled bottle diameter, stem diameter, and bottle length. A tapered microfiber with a 2 µm waist diameter was used for coupling, enabling the resonator to achieve a high quality factor (Q > 1.5×10⁵), confirming its low-loss performance and strong field confinement. Honey samples with concentrations ranging from 10% to 60% were analysed. The MBR sensor demonstrated a sensitivity of 0.0824 dB/% with excellent linearity of 97%, while wavelength-shift analysis showed an additional sensitivity of 4.0 pm/%. The sensor exhibited stable and repeatable responses across multiple experimental cycles and short-term stability tests. Compared with conventional techniques such as refractometry, FTIR, and electrochemical methods, the MBR offers significant advantages in compactness, non-destructive measurement, and sensitivity. These findings establish the MBR as a reliable platform for honey quality monitoring and authenticity testing, with potential for broader food and industrial sensing applications.