Design analysis of Bloch surface wave based sensor for haemoglobin concentration measurement

In this paper, a Bloch Surface Waves (BSW) based sensor is proposed to estimate the haemoglobin concentration in human blood. The behaviour of the sensor is analysed using a transfer matrix method. The proposed structure is designed considering one-dimensional photonic crystal, where a defective top layer is deliberately introduced to confine a surface plasmon-like mode called Bloch mode at the top interface. The effective refractive index of top interface changes along with haemoglobin concentration. Thereby, monitoring the angel of incidence to confine BSW mode can helps in determining the haemoglobin concentration. The sensing capability, FWHM and figure-of-merit of the proposed structure are improved by optimizing the defect layer thicknesses, incident angels and wavelengths. Proposed structure shows an average FWHM and average sensitivity of around 0.00508 and 0.0133 degrees/(g/L) respectively.