Multichannel Integrated Fiber-Optic End-Face Sensor for Deuterium Detection from Hydrogen Via Flow-Temperature Synergistic Regulation.

Inspired by the selective adsorption and separation technology of isotope gases using porous materials, this work reports the first successful realization of optical fiber-based deuterium (D2) sensing in the presence of hydrogen (H2). Initially, we propose a novel three-core fiber (TCF) end-face sensor integrating two microtips and a plasmonic metasurface on its end-face, enabling simultaneous sensing of three parameters: temperature, flow velocity, and gas concentration. Specifically, the two microprobes form two Fabry-Pérot (FP) cavities; the glass microprobe is used for flow velocity sensing, while the polymer microprobe acts as a temperature sensor. Additionally, a sensitive film composed of a hybrid material─palladium nanoparticles loaded onto a crystalline porous organic framework (Pd-COF)─is coated onto the metasurface. By exploiting the specific adsorption of Pd-COF toward H2/D2 and the spatial confinement enhancement effect, highly selective D2 detection is achieved. Investigations on sensing performance under different flow rates and temperatures show that at 0.6 m/s and 80 °C, the D2 detection sensitivity reaches 0.183 nm/ppm, with a D2/H2 separation factor of approximately 12.04. The discrimination and detection of isotope gases in optical fibers realized by means of environmental regulation is of great significance for expanding the scope of optical fiber sensing technology.