Thin Film Waveguide Sensor for Measurement of the Absorption Coefficient of Hemoglobin Derivatives

A simple method for determining the absorption coefficient of oxyhemoglobin and deoxyhemoglobin in human blood is proposed. The method is based on a variation of the complex propagation constant of guided wave in a thin-film optical waveguide. On the waveguide layer, a serial multi-channel sample chamber is constructed to vary the interaction length between the evanescent field and the sample, and the dependence of the sensor response on the interaction length is investigated for various concentrations of two hemoglobins. The response of this sensor is linearly proportional to the interaction length and the concentration of the two hemoglobins. The attenuation constant due to the evanescent field absorption between the channels is experimentally obtained with the designed sensor, and the absorption coefficient is determined by the proposed method. The determined absorption coefficients coincided with those obtained by conventional transmission measurement.