Integrated refractive index sensor based on hybrid coupler with short range surface plasmon polariton and dielectric waveguide

In this paper, an integrated sensor based on the vertical hybrid coupler composed of a short range surface plasmon polariton (SRSPP) waveguide and a SiNx dielectric waveguide has been studied theoretically and experimentally in detail by varying the structure parameters and the thickness of detection layer. It is demonstrated that the output power of the sensor changes significantly with the refractive index of the detection layer and the resolution is estimated to be as high as 7.3 × 10−6 refractive index units. The sensing range can be adjusted coarsely and delicately by varying the thickness of SRSPP waveguide and the width of the SiNx waveguide, respectively. Owing to the highly bounded mode field of SRSPP, the sensor is also applied to detect a 5 nm-thick variation of detection layer with thickness detection sensitivity as high as 0.67 dB/nm. Further, the sensor is used to detect the bisphenol A.