Study On Plasmon Waveguide Resonance Sensor Using An Au-MgF₂ Structure

Surface plasmon resonance(SPR) is an optical sensing method offering high sensitive refractive index(RI) measurement, which have been widely used in the biological and chemical applications for label-free sensing. In order to achieve high performance, optimization of SPR sensing system is developed and plasmon waveguide resonance(PWR) sensor based on SPR has been proposed. PWR sensor has narrower angular resonance curves, higher electric field strengths and longer penetration lengths and depths compared with the conventional SPR sensor, hence has wilder dynamic range and higher refractive index resolution. PWR sensor is suitable for bulk measurement and detecting large biomaterials due to its unique properties.In this work, we propose PWR sensor using an Au-MgF2 structure. Comparing to the symmetrical optical waveguide(SOW) with MgF2/Au/MgF2 layers, this PWR structure is insensitive to the thickness of the metallic layer, so the exact matching of layers are not needed. The refractive index resolution is higher than that of the Au/ SiO2 layered PWR due to the lower refractive index of MgF2 compared with SiO2. Calculation and experiment substantiate that this structure can exceed the performance of the conventional SPR sensor based on Kretschmann configuration in fluid analyte.This PWR structure is less sensitive to the thickness of the metallic layer compared with SOW and can be built by a simple and convenient process, making it an easy, low cost and practical sensing structure for sensitive and accurate analysis, which has potential in the biological and chemical applications.