[OPTICAL REVIEW Vol. 5, No. 4 (1998) 257-261]

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

Kyungho KIM,1 Shinwon KANG,2 Kunihiro MATSUMOTO1 and Haruyuki MINAMITANI1

1Department of Biomedical Engineering, Faculty of Science and Technology, Keio University, Hiyoshi, 3-14-1, Yokohama, 223-8522 Japan, 2The S.T.R.C., Kyungpook National University, Taegu, 702-701 Korea

(Received April 6, 1998; Accepted June 12, 1998)

A simple method for determining the absorption coeffcient 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 coeffcient is determined by the proposed method. The determined absorption coeffcients coincided with those obtained by conventional transmission measurement.

Key words : waveguide, evanescent field, hemoglobin, optical sensor, thin film