Mid-infrared power measurement using the photothermal effect of TiO₂ microparticles in a fiber-optic Fabry-Pérot interferometer

Abstract This research explores the feasibility of using the photothermal effect in TiO 2 microparticles (MPs) to measure mid-infrared (MIR) laser output power, introducing a new application of the photothermal effect in MPs. The MIR power measurement setup is based on an optical fiber-based Fabry-Pérot interferometer (FPI) structure, which includes a silica fiber ferrule, a polymer layer, a TiO 2 MP layer, and a ZBLAN fiber ferrule. The power of a 1550 nm probe beam in reflection mode of the FPI configuration was found to change linearly with 2.7 μ m laser output power due to the photothermal conversion effect in the TiO 2 MPs. The MIR laser output power was indirectly measured by detecting changes in the reflected 1550 nm probe beam power with a low-cost 1.5 μ m InGaAs/InP-based optical power meter. This setup could measure MIR optical power in a range from 0 to 2 mW.