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

Abstract

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 rdual=I2/I1 is used as the detector response and is related to the absorbing species. A reference curve rdual(C) obtained by calibration serves to determine concentrations of the component. It has been theoretically shown and experimentally verified that the curve rdual(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

On the Capability of Artificial Neural Networks to Compensate Nonlinearities in Wavelength Sensing

“…In principle, the absorption of visible light in the silicon bulk induces generation of electron-hole pairs; where the generation rate depends on the wavelength of the incident light and on the depth from the silicon surface. Therefore, three stacked junctions result different spectral responses depending on the junction depth [1,21,22]. Figure 2 shows an example of BJT spectral response given at room temperature, the characterized cell is fabricated using 1.2 μm standard BICMOS process with an area of 28 by 28 μm [1].…”

Quality monitoring of flowing water using colorimetric method based on a semiconductor optical wavelength sensor

“…When a dual-wavelength light-source is employed and Eq. (4) is considered, the photocurrent ratio can be written as [7] R dual ¼…”

“…In recent years, the BDJ (buried double p-n junction) optical wavelength sensor has attracted much attention in colorimetric measurements such as iron concentration measurement [7] and seawater pH determination [8]. In those reports, a dual-wavelength light-source (i.e., two LEDs) was employed, chemical agents were added into the solutions, and the iron concentration or PH value was determined by measuring the chroma of the reaction output [7,8] wavelength can be absorbed by the colored solutions and the changes of effective wavelength of the transmitted dual-wavelength light can be measured by the sensor.…”

“…In those reports, a dual-wavelength light-source (i.e., two LEDs) was employed, chemical agents were added into the solutions, and the iron concentration or PH value was determined by measuring the chroma of the reaction output [7,8] wavelength can be absorbed by the colored solutions and the changes of effective wavelength of the transmitted dual-wavelength light can be measured by the sensor.…”

“…When the monochrome light penetrates into the window of the device, its absorption gives rise to the two photocurrents I 1 and I 2 , flowing respectively through the shallow and deep junctions. These two currents can be written as [7] I 1 ðkÞ ¼ PðkÞS 1 ðkÞ ð 1Þ…”