Research Projects

Rationale: The proposal is motivated by the need to understand and control electromagnetic hotspots at sub-wavelength scales, which are crucial for advancing nanophotonic applications. Plasmonic nanoparticles and meta-molecules can concentrate electromagnetic fields into nanoscale regions, creating hotspots with significant potential for sensing, energy harvesting, and nanophotonic technologies. However, controlling and harnessing heat at the nanoscale remains a challenge. Recent developments in optical assembly, specifically trapping and tweezing, have enabled the manipulation of nanoparticles using light. Optical binding, which involves electromagnetic interactions between particles, is an important area in optical trapping. The emergence of optothermal binding introduces a new paradigm, where thermal gradients induced by light can bind and organize plasmonic matter. This proposal seeks to study the optothermal binding of plasmonic matter, exploring how these new interactions can be controlled and utilized. Background: Plasmonic assembly has traditionally relied on conventional methods, such as chemical synthesis or lithography, to organize nanoparticles. Optical binding has become a significant area within optical trapping, allowing for the assembly of particles through light-induced electromagnetic forces. More recently, optothermal trapping has emerged, where localized heating from light absorption creates temperature gradients that can manipulate nanoparticles. Our laboratory is one of the few in the world that has been creating and studying optothermal assembly of colloids at scales down to a few hundred nanometers. These new developments open up possibilities for dynamic and reversible assembly, but the fundamental behavior of electromagnetic hotspots in optothermally bound systems is not yet understood. Objectives 1. To experimentally probe and image the electromagnetic hotspot in optothermally bound plasmonic matter, supported by theoretical analysis and simulations. 2. To investigate hot Brownian dynamics, focusing on the stochastic noise introduced by optothermal perturbation. 3. To analyze spectral fluctuations in both real and momentum space, examining elastic and inelastic scattering processes that influence the stability and functionality of plasmonic assemblies. Novelty: Optothermal binding represents a new concept in the field of nanoparticle assembly. The behavior of electromagnetic hotspots in such bound states has not been explored. Understanding spectral fluctuations in these systems has direct implications for the design of reconfigurable metamolecules. Furthermore, the findings are expected to impact studies in statistical optics and provide a foundation for addressing decoherence effects, which are relevant for the development of classical, quantum, and biological sensors.