Hybrid Microtip-Based Thermal Anemometer With Harmonic Vernier Effect on Fiber-Optic End Face

The fabrication of an ultra-compact, highly sensitive anemometer on a hundred-micron fiber end face poses a formidable challenge. Traditional thermal anemometers often sacrifice low power consumption and temperature control for enhanced range and sensitivity. To overcome these limitations, we introduce a microtip-based thermal anemometer seamlessly integrated with optical fiber ends. First, a SiO₂ microtip was prepared by the discharge melting tapering technique. Subsequently, a polymer microtip doped with photothermal material was further grown on the SiO₂ microtip by photo-induced polymerization. This dual-layer microtip structure forms a cascade of Fabry-Pérot interferometer (FPI) and increases the sensitivity by approximately 10.8 times based on vernier effect. Zr-PDI is a metal-organic framework (MOF) with a photothermal efficiency of 52.3%, which can reach 113°C under 1.96 mW (808 nm) laser irradiation. Experimental results demonstrate that the sensor achieves the wind speed detection range of 0–20 m/s, with a maximum sensitivity of 7.36 nm/(m/s) in the range of 0–3 m/s. This low-power, ultra-compact sensor features highly sensitive, wide-range wind speed measurement capabilities.