Quantitative Polarimetric Study of Scattering from Localized Nanoparticles

Lakhotia, Harshit (2014) Quantitative Polarimetric Study of Scattering from Localized Nanoparticles. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Harshit Lakhotia) Harshit_Lakhotia.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Plasmonics which is the study of oscillation of free electrons in metallic structures is widely studied these days both from the point of view of understanding the basics of light matter interaction and its applications in the area of sensing, detection, labelling, wave guiding, surface enhanced Raman spectroscopy, opto-electronics etc. One particular area which is not being studied in particular is the Polarimetric studies of scattering from Plasmonic nanostructures. This thesis consist of development of setup for the studies of scattering from plasmonic nanostructures such as silver nanoparticle. We have tried to build a dark field microscope for quantitative Mueller matrix polarimetric study from Plasmonic nanostructures. The microscope was calibrated using eigenvalue calibration method. To the best of our knowledge this is the first attempt to develop a fully calibrated polarimetric system to do polarization studies from microscopy. Since we are interested in studying the scattering from plasmonic nanostructures we in particular chose dark field microscope for the purpose. Dark field polarimetry microscopic imaging set up consist of polarizer, and quarter wave plate(QWP) attached between tungsten lamp and sample chamber in inverted dark field microscope and act as a polarization state generator(PSG). Similar arrangement of polarizer and QWP in reverse order was placed between output of microscope and spectrometer, this arrangement acts a polarization state analyzer (PSA). We calibrated the system both for dark field and bright field condenser. Developed system was initially explored to study the dynamics of formation gold nanorods. Mueller matrix both from bulk and microscope of growing gold nanorods were taken at different time. The change in polarization parameter with increasing size of nanorods was studied. Trends were comparable with the numerically obtained polarization parameters for silver nanorods. We had earlier showed that diattenuation parameter peaks at points where resonant modes are present and retardence parameters peaks where there is intereference of modes. The same trend was experimentally verified by studying the scattering from gold nanorods. Further investigation on specially manufactured nanostructures exhibiting fano resonance will be done. Since Fano resonance occur due to interference of two modes it can be probed using the retardence parameters. Future work will also comprise of studying SH GH shifts using the experimentally obtained diattenuation and retardence parameters.

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