Investigating Chiral Responses in Plasmonic Nanostructures

Sarkar, Meghna (2025) Investigating Chiral Responses in Plasmonic Nanostructures. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Meghna Sarkar (20MS119)) 20MS119_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (37MB)

Abstract

Detection of chirality using light-matter interaction has become a rapidly growing research field nowadays since it has been used in various aspects such as drug detection, research on bio-molecules, photonics etc. In this regard, this thesis explores a novel technique in the field of chirality detection in plasmonics using two optical methods - Fourier imaging and Mueller matrix polarimetry. Fourier imaging is implemented to overcome the limitations of real-plane imaging and it offers a powerful approach for characterizing chirality of the samples using their polarization properties. From analyzing Fourier imaging data, important information about structural and compositional features of the sample can be extracted. On the other hand, Mueller matrix polarimetry offers a comprehensive and robust description of polarimetric information about the light-matter interaction. In this thesis, we have proposed that the chirality signature can be detected in the farfield domain using plasmonic metasurfaces, which has not been explored yet. The far-field intensity distribution of chiral light-matter interaction has also been achieved using simulation. In experiments, this not only overcomes the limitations of near-field imaging, but also using Fourier imaging it is possible to enhance the noise-level chiroptical response by a significant order. The chiroptical signals can also be differentiated from other polarization responses using Mueller matrix decomposition. Varying thickness of the nanostructure offers an outstanding tunability for the chiroptical response. Presence of polarization singularity in the experimental measurements is also a key finding which gives a strong motivation for future research in this domain. These findings already give a profound indication that this technique can be used as a potential replacement of the conventional spectroscopical approach.

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