Optical and Thermal Nonlinearities in Laser Trapping of Metallic Metal Dielectric Hybrid Nanoparticles and Laser Beam Shaping with a Spatial Light Modulator Theories and Experiments

Abstract

In recent years, there is an impetus to explore the intriguing physics of nonlinear newlineoptical and thermal forces acting on particles of varying sizes under femtosecond pulsed newlineexcitation. The immense peak power of ultra-short pulses introduces optical nonlinearity (for newlineexample, optical Kerr effect) as well as thermal nonlinearity that promise to hold the capacity newlineto fine-tune the nature and the magnitude of trapping forces, and thereby control the trapping newlinedynamics. Such nonlinear phenomena become more fascinating for particles made of materials newlinewith plasmonic characteristics, especially due to the distinctive size-dependent plasmonic newlineresonance features inherent to nanoparticles, quite different from their bulk counterparts. On newlinethe other hand, laser beam shaping techniques are gaining increased attention in modulating newlineoptical forces with structured light, and controlling of gradient and scattering forces with the newlineaid of such structured light is thought-provoking. This thesis focuses on the theoretical and newlineexperimental investigations of the effects of optical and thermal nonlinearities in laser trapping newlineunder femtosecond pulsed excitation, and additionally, on the application of shaped laser newlinebeams in optical trapping and manipulation. newlineFollowing an introduction to the motivation behind this work and an overview of the newlinemethodologies used, in the first part of the thesis, theoretical results describing the effects of newlineoptical nonlinearity on trapping of silver nanoparticles, silver-polystyrene core-shell type newlinenanoparticles, and dielectric/metal-dielectric multi-layered type nanoparticles will be newlinediscussed. Further, the effects of the surrounding medium (having high Kerr nonlinearity) on newlinebeam propagation and trapping will be presented. In the subsequent section, theoretical results newlinedescribing the effects of optical and thermal nonlinearities on the trapping dynamics of newlinepolystyrene particles of varying sizes at distinct axial trapping planes will be discussed. In the newlinesecond part of the thesis, generation and propagation o