Microstructured fiber based plasmonic index sensor with optimized accuracy and calibration relation in large dynamic range

A novel surface plasmon resonance photonic sensor is proposed using an index-guided microstructured fiber with an analyte channel introduced into the central core. Compared with the previous designs of porous fiber core, variation of the signal amplitude with exterior refractive index is demonstrated to be contrary to that of the sensitivity in the proposed fiber, contributing to optimized detecting accuracy over a large refractive index range of 1.33 to 1.42. By carefully choosing the central channel size, the analyte-filled core can achieve narrower resonance spectral width and higher signal to noise ratio (SNR) than the air-filled core. Sensor responses are also studied in this paper based on two spectral interrogation methods, including monitoring single resonance shift and measuring change in the resonance separation. For both methods, response linearity has been improved considerably through partially filling the core with analyte. The maximal sensitivity reaches 10− 6 refractive index unit (RIU). The linear sensing performance along with the broad measurement range is very promising in the application of the proposed sensor as sensitive refractometer.