A study of the polarimetric characteristics of planar chiral mesoscopic structures
It has been shown previously that chiral materials can rotate the direction of incident polarized light. This work focuses on a new way of investigating the polarized response of chiral metamaterial structures and nanoparticles. In the theoretical part of this work, fundamental concepts related to chirality are defined. Previous contributions to quantify the chirality of planar shapes are reviewed. The prospects of different expressions based on triangle models are highlighted.A dual photo-elastic modulator incorporate with lock-in amplifier techniques is used to measure the polarization states alteration. Subsequently, the polarization states are mathematically analyzed using Stokes parameters and Muller matrices. In order to minimize the measurement time, the microscope polarimeter was optimized by using LabView to collect the experimental data and using Python for analyzing the data during the overdetermined calibration process and the sample measurements.Furthermore, a dual photoelastic modulator-based Stokes polarimetric microscope is developed in the laboratory and used to study the polarization states locally at the sample surface level. The polarimetric imaging system provides quantitative measurements of the four Stokes parameters and hence enabling the determination of the full polarization states across the focusing plane. Subsequently, the technique allows us to quantify the polarised component's intensity, the depolarized component, the degree of polarization, the degree of linear polarization, the degree of circular polarization, the polarization orientation, and the elliptical angle.The developed polarimetric microscopy is applicable to a wide variety of structural studies and provides insightful information about the samples. Through the experimental study in transmission mode, the result of several selected samples is presented (i) chiral metamaterials and (ii) achiral metamaterials, (iii) copper nanoparticles and (iv) gold nanoparticles.
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