OP: Building Artificial Photonic Materials from Nanoscale Optical Matter

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Nontechnical description: Photonic materials are patterned constructs consisting of particles, smaller than the wavelength of light, that are artificially bound together in various ordered arrangements. By varying the size, shape and periodic arrangement of the particles it is possible to control material optical properties such as color, shine and even the absorption of light. This project aims to design and build photonic materials comprising particles that are only a few nanometers in size. This is accomplished by shining light onto a fluid containing numerous metal nanoparticles. Analogous to the process of atoms joining to form molecules, the metal nanoparticles bind together in the fluid to form arrangements of particles. By varying the flow of the fluid it is possible to control the structure of these photonic materials, and therefore their optical properties. A combination of computer simulations and experiments provide a rich environment for training undergraduate and graduate students. Incorporating components of the research into existing undergraduate courses and laboratory experiments enables students to develop a deeper understanding of a wide range of materials-related concepts. Technical description: Optical matter represents a unique material arising from pure mesoscale electrodynamic interactions of colloidal particles in an optical field. Due to significant instabilities associated with nanoparticle-comprising optical matter, previous studies have predominately addressed microparticle-based structures. This project aims to eliminate the inherent instability problem and create a paradigm for constructing artificial photonic materials using nanoscale optical matter. The paradigm relies on advanced laser beam shaping techniques and significant mesoscale electrodynamic interactions among strongly scattering plasmonic metal nanoparticles in optical fields. Efficient simulation models are developed to elucidate the collective electrodynamic interactions of multiple nanoparticles, to reveal the equilibrium binding configurations. Optimized optical fields are created to increase the spatial and temporal stability of the nanoscale optical matter. Optical-matter-embedded polymer microparticles are further fabricated in microfluidic channels by photopolymerization. These hybrid particles can serve as building blocks for two- or three-dimensional metal-dielectric superlattices, leading to new types of photonic materials with tailored optical properties.