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In this work, we report on the application of the polarization modulated spectroscopic ellipsometry-based surface plasmon resonance method for sensitive detection of microorganisms in Kretschmann configuration. So far, rotating analyzer and single wavelength polarization modulation methods have widely been investigated for phase sensitive surface plasmon resonance measurement. In this study, a much simpler optical setup relying on fast electro-optic phase modulator crystals is introduced for bacteria detection. A beta barium borate crystal connected to a function generator is adapted for generating phase shifts in the millisecond regime to extract the ellipsometric angles ( Ψ and Δ ) under the surface plasmon resonance condition. For detection, the gold surface was functionalized with anti-Escherichia coli antibodies, and E. coli K12 was attached to them. We show that polarization modulated spectroscopic ellipsometry achieves a refractive index resolution in the order of 10 - 5 RIU, and a limit of detection of 10 2 CFU/mL for E. coli K12 which is compatible with other surface plasmon resonance based phase sensitive methods with more complex detection concepts. As a follow-up step, an optical model can be developed to enhance this biosensor's performance, and applications for sorting and detecting other biological targets will be investigated., (© 2024. The Author(s).)

As developed countries' ability to control infectious diseases increases, it has become clear that genetic diseases are a major cause of disability, death, and human tragedy. Coronavirus has recently spread throughout the world, and the capacity to detect low concentrations and virus changes can help to prevent the sickness from spreading further. In this paper, a surface plasmon resonance sensor based on nanostructured thin films and graphene as a 2D material has been designed with high sensitivity and accuracy to identify DNA-based infectious diseases such as SARS-CoV-2. The transfer matrix method assesses the effects of different structural factors, including nanolayer thickness on the sensor's performance. The results demonstrated that the sensor with the Kretschmann configuration has ultra-high sensitivity (192.19 deg/RIU) and a high figure of merit (634.68 RIU -1 )., Competing Interests: Competing InterestsThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2022.)