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Sensitivity Optimization of Kretschmann's Optical Sensors

Abstract:

Optical sensors based on Kretschmann's configuration are extensively used in many sensing fields. Usually, this three-medium system is designed in such a way that the optical excitation of surface plasmon resonance (SPR) can be achieved. In particular, they can work as fast quasi-point sensors if they are operated at a fixed wavelength and fixed angle of incidence. Therefore, for quasi-point sensors, the greatest sensitivity is reached at an angle of incidence different from the total attenuation one but where the slope of the reflectivity curve is the greatest. In this work, finding the point of greatest sensitivity for Kretschmann's configuration is proposed without forcing the reflectivity curve to have an angle of incidence and thickness at which surface plasmon resonance can be excited. In order to demonstrate this, the point of greatest sensitivity is determined as a problem of optimization from the reflectivity function without introducing the full constraints that surface plasmon excitation requires. The obtained results were compared and analyzed through eighteen case studies against the results obtained in previous work. It was shown that the optimization method, in general, leads to a significant increase in the sensitivity of this type of optical sensor and that this effect is enhanced for wavelengths in the infrared range.