A dual-wavelength method using the BDJ detector and its application to iron concentration measurement

A new and uncomplicated method for absorption detection is presented that requires no optical instrument such as a spectrophotometer or colorimeter. It makes use of a two-wavelength light source and a BDJ (buried double p-n junction) detector operating as wavelength-sensitive device. The intensity-insensitive photocurrent ratio r_dual=I₂/I₁ is used as the detector response and is related to the absorbing species. A reference curve r_dual(C) obtained by calibration serves to determine concentrations of the component. It has been theoretically shown and experimentally verified that the curve r_dual(C) becomes linear at low concentrations. Through an investigation in the case of iron concentration measurements, the suggested method has proved to be sensitive and reliable.

Keywords: BDJ detector, dual-wavelength method, absorption detection, concentration measurements