Plasmonic Fiber-optic Photothermal Anemometers with Carbon Nanotube Coatings

We propose and demonstrate an ultra-sensitive plasmonic fiber-optic hot-wire anemometer. This instrument comprises a highly tilted fiber Bragg grating-assisted surface plasmon resonance (SPR) sensor, which is coated with carbon nanotubes as the photothermal conversion element. The carbon nanotubes on the sensor surface efficiently convert light from the heating laser, of which wavelength matched to the SPR window, into heat, thereby setting the sensor in an elevated temperature state. Air flow draws away surface heat, thus inducing both a strong SPR wavelength shift and power modulation. Using this anemometer, we experimentally achieve a dynamic range of 0.05 to 0.65 m/s for wind speed measurement. Furthermore, we demonstrate real-time monitoring of wind speed by measuring the intensity of the heating laser. This sensor is simple and robust in structure. It has a wide range of potential applications in both scientific research and industrial production.