Femtosecond laser micromachining triple-modality optical fiber sensor with multiband optical decoupling for simultaneous dual-biomarkers and temperature monitoring

To address the insufficient information from single-parameter biological detection, this study proposes a multi-parameter optical biosensing scheme based on femtosecond laser micromachining (FLM), enabling simultaneous detection of creatinine, urea and temperature monitoring. Without damaging the main structure of the optical fiber, FLM modifies its internal structure to achieve precise waveguide fabrication, refractive index (RI) regulation and cladding mode coupling. On this basis, Mach-Zehnder interferometry (MZI), surface plasmon resonance (SPR, for biological signal detection) and fiber Bragg grating (FBG, for temperature detection) are integrated into a single microstructured optical fiber (MOF). The system is analyzed via detailed theoretical simulation: the RI sensitivities of SPR and MZI are 1842 nm/RIU and 516 nm/RIU, respectively, while their temperature sensitivities (along with FBG) are - 0.242 nm/℃, - 0.054 nm/℃ and 0.012 nm/℃. By combining specific sensitive materials with microfluidic chip channels, an MZI urea detection channel, an SPR creatinine detection channel and an FBG temperature monitoring mechanism are constructed. Experimental results show the structure can monitor temperature and has good selective detection capability for creatinine and urea, with sensitivities of 7.2 nm/mM and 3.8 nm/mM, and limits of detection (LOD) of 0.07 mM and 0.09 mM, confirming its excellent dual biological indicator detection performance.