High Sensitive Measurement Of Concentration Based On Optical Waveguide Resonance Technology

The function of optical biochemical sensors is to transfer biological or chemical signals to the optical signals which can be measured qualitatively or quantitatively. These biochemical information can be monitored by acquiring the optical information. Owning to many advantages such as high sensitivity, real-time and quickly reacting, the optical biochemical sensors have been used in many different areas such as agriculture, medicine, environment, food industry and diagnosis.In this article we tell some theory on the usual plane waveguide, and make analysis on the double-sided metal coated waveguide especially. The special structure of double-sided metal coated waveguide make it have a broad range of effective refractivity index, which make the incident light can be coupled in the waveguide directly. The millimeter guide layer can make the samples injected into the waveguide easily. Besides the ultrahigh-order guided modes existing in the guide layer can be used as the extremely sensitive probs. These properties let the double-sided metal coated waveguide made to a high sensitive oscillation field sensor, which is more sensitive than the traditional evanescent field sensor such as the SPR sensor.In this article we used this sensor to do concentration detecting. Being different from the previous concentration measuring method used with this sensor, we detect the concentration by sensing the imaginary part of the refractivity index of samples. We have make analysis on the sensitivities of sensors in our experiment. And make the simulation on the ATR spectrum of the waveguide used in the experiment. As the imaginary part of the refractivity index of samples mainly affect the up-and-down movement of the ATR spectrum, the method which detect the imaginary part of the refractivity index have high sensitivity.The concentration detecting sensor system was made based on the double-sided metal coating waveguide, which include the design of optical system, mechanical system, control circuit and software and so on.In the experiment various glucose solutions were measured with our sensor. The glucose solutions have been colored in order to detect the imaginary part of the refractivity index. As the absorbance of the solution is proportional to the concentration of solution, the concentration of solution can be determined by measuring the change of the ATR absorption peak. As a comparison the glucose solutions are also measured with the spectrophotometer under the same conditions. The results show that the sensor can detect the0.111mmol/L concentration difference of the solution, which is much better than the spectrophotometric method. Some factors which can affect the sensitivity of the sensor are also analyzed, as well as the measuring results of the KH2PO4using our sensor. At last some advices which can improve the performance of the sensor are mentioned.The sensor in this article have simple structure and high sensitivity. It will have high application values in many areas.