Absorption spectroscopy in scattering samples using integrated optics

Conventional spectrophotometric methods for measuring the concentration of light-absorbing material in a sample require that the sample be transparent. If scatterers are present they disturb the absorption measurement. An example of this sort is the determination of the constituents in blood plasma. Red blood cells interfere with a direct optical measurement if they are not removed. Theory and experimental results are presented for an integrated optics device which can perform absorption spectroscopic measurements of blood plasma with scatterers present. For a device which measured plasma bilirubin concentration, guided wave attentuation of less than 0.01 dB/cm due to red cell scattering was observed.