Robust design of Kretschmann plasmonic PCW-based integrated biosensor circuit

This paper presents the design optimization of an Integrated Biosensor Circuit (IBC) which utilizes graphene-based plasmonic Photonic Crystal Waveguide (PCW). The effects of 5 input signals, 4 control factors and 1 noise factor were investigated using Taguchi's dynamic L9 orthogonal array where the input signals are linearly related to the output response. The focus is to find the best combination of the parameters to achieve the best linearity insensitive to noise and obtain a robust design of the IBC. The input signals are based on the Refractive Index (RI) of glucose concentration in urine which ranges from 1.335 to 1.341. The control factors of the IBC are the PCW length (μm) – Factor A, the waveguide Bragg grating (WBG) length (μm) – Factor B, the modulator P length (μm) – Factor C, and the modulator Q length (μm)-Factor D, whereas the noise factor is the delta temperature of modulator Q where each factor was evaluated at 3 level values. Taguchi’s Higher-the-Better signal-to-noise (S/N) ratio was used to maximize the Free Spectral Range (FSR) of the IBC’s reflection output power which will directly increase the IBC’s biosensing sensitivity. The dominant control factors were identified as the PCW length (43% factor effect) and the WBG_2 length (22% factor effect). Upon dynamic Taguchi optimization, the FSR of the IBC improved by 0.62 dB for S/N ratio for linearity, the best control factors is A1B1C1D2, and the IBC’s sensitivity improved to 8.86μm/RIU for detection of glucose concentration in urine.