An optical fiber-waveguide-fiber platform for ppt level evanescent field-based sensing

Photonic sensing has always encountered problems such as enhancements of light-analyte interaction and signal collection efficiency. In this study, we propose an optical fiber-waveguide-fiber (OFWF) sensing platform, which comprises a non-cladded polymer waveguide sandwiched by two multimode optical fibers coaxially fabricated by laser-induced self-written waveguide (LISW) technique. The sensing platform not only provides a highly effective and versatile evanescent field (EF) based probe, but also possesses three orders of magnitude higher sensing signal collection ability than that of microscopic systems. A typical chromophore rhodamine B (Rh B) was used to verify the capability of the sensing platform, and a limit of detection of 10−12 g/ml level in fluorescent measurement was demonstrated without using any enhancement approaches. The sensing platform is compact and low cost, which can be utilised for various highly sensitive photonic sensing applications.