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

This research explores the feasibility of using the photothermal effect in TiO₂ 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 TiO₂ 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 μm laser output power due to the photothermal conversion effect in the TiO₂ 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 μm InGaAs/InP-based optical power meter. This setup could measure MIR optical power in a range from 0 to 2 mW.