Study of Linear and Nonlinear Optical Interactions of Micro/Nanoparticles Embedded in an Organosiloxane Matrix

Light and matter interactions at the nanoscale have gained huge attention due to their increased scientific importance and technological relevance. Nanomaterials are excellent candidates for photonic and optoelectronic applications because of their quantum confinement effects and high surface-to-volume ratios, thereby enabling us to control light by altering their physical and chemical properties. Maxwell’s equations well-describe the physical phenomena of light-matter interactions, where the dielectric polarization is subject to drastic changes with respect to the incident optical field intensity. Such variations can lead to significant changes in optical and thermal properties of nanomaterials. Recent research into the interactions between light and matter has mainly focused on understanding electronic, photonic, and phononic properties of nanomaterials.

This dissertation addresses chemical functionalization and self-assembly of nanoparticles, and how matter behaves under low and high intensity light. Excessive heating in buildings due to solar irradiation falls under the category of low-intensity effects, while high-intensity light, in particular lasers, are capable of causing damage to eyes, optical sensors, and include recent threats to air traffic in the US. We explore the properties of various nanoparticles, including titanium dioxide (TiO2), graphene oxide (GO), and silver nanoparticles (AgNPs), and incorporate them into a stable transparent organosiloxane matrix. Owing to the high refractive index and high band gap, a TiO2 nanoparticle scatters light efficiently across the entire solar spectrum, making it an ideal candidate for a solar reflective coating. Strong nonlinear scattering, together with strong broadband and specific wavelength absorption properties, make GO and AgNPs excellent options for optical limiting devices, which have a high optical transmittance for normal light, but allow a significantly low transmittance at higher intensities.

We have seen a >10% (4.1 oC) reduction in the internal temperature of concrete treated with a TiO2 coating, and nonlinear absorption coefficients of 378 and 277 cm/GW for functionalized GO and AgNPs, respectively, which are significantly higher than previously reported values. Both the linear and nonlinear effects caused by light interactions within nanomaterials can be explained through Maxwell’s equations, and the scope of nanomaterial use is quite varied depending on need.