Photothermal anemometer based on carbon nanotube-coated highly tilted fiber Bragg grating-assisted SPR sensor

An ultra-sensitive plasmonic fiber-optic photothermal anemometer is proposed and demonstrated. The device consists of a highly-tilted fiber Bragg grating (TFBG) sensor, which is coated with a gold layer exciting surface plasmon resonance (SPR) and then carbon nanotubes as the photothermal conversion element. The carbon nanotubes deposited on the sensor surface efficiently convert light from the heating laser, which is wavelength matched to the SPR signature, into heat. Air flow draws away the surface heat, thus inducing both a strong SPR wavelength shift and a changed of the power modulation. Using this approach, the proposed anemometer accounts for a dynamic range from 0.05 m/s to 0.65 m/s for wind speed measurement. In addition, the real-time monitoring of wind speed has been proved by measuring the intensity of the heating laser source. This device is a valuable candidate for a wide range of potential applications in both scientific research and industrial production, given its simplicity and robustness in structure.