Evaluation Numerical Methods Effectiveness for Processing of Measurement Results by Improved SPR-Sensor

Abstract

In this work there has been investigated the effect of electron beam treatment of the glass substrates surface of sensors based on surface plasmon resonance phenomenon with active gold based layer on the accuracy of determining the angular position of the reflection characteristics in case applying numerical methods for processing direct measurement results: approximation by polynomials of the 2nd 3rd and 4th degrees and processing by midline method. Sensors with different specific powers of electron beam treatment of glass substrates were investigated: 0, 27, and 36 W/mm2. The reflection characteristics for the gold-air interface were investigated. According to the results of experiments and numerical analysis, it was found that the effect of electron beam treatment on the change in the absolute error in determining the minimum reflection characteristics substantially depends on the chosen numerical method. Thus, the improved midline method provides a 6-fold decrease in the absolute measurement error compared to the midline method for samples without processing and almost 12 times for samples with processing power of 27 W/mm2. Moreover, for this method, the smallest absolute error is observed for the power of electron beam treatment 36 W/mm2 and is 0,58 arc sec., which indicates the appropriateness of applying new method. Compared to the approximation methods by polynomials and the midline method, the improved midline method has greater accuracy in determining the minimum reflection characteristics because it depends less on not only its symmetry associated with the optical characteristics of the gold-air transition layer, but also on changes in the intensity of reflected light minimum reflection characteristics. According to the results of calculations based on predefined optical constants from the measured reflection characteristics, it was found that, with a higher irradiation power, the symmetry of the reflection characteristic, the propagation distance and the penetration depth of surface plasmons increase, which is associated with a decrease in surface roughness after electron beam treatment and, as a consequence, a decrease in attenuation fields of surface plasmons. Research can be useful in the development of sensors based on surface plasmon resonance phenomenon and methods for processing measurement results