Chemical approaches to controlling light propagation

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The Saravanamuttu Group examines ways of controlling light propagation through (i) optical self-trapping phenomena and (ii) microperiodic structures with bandgaps for visible light. Research in both fields is stimulated by demands for new optical fibre-free ways to guide light. (i) self-trapping occurs when a light beam that normally diverges induces its own waveguide and propagates as a bound solution (optical mode) of this waveguide. Self-trapped beams and their extraordinary particle-like behaviour have potential in next-generation optical devices in which self-trapped beams (carrying data signals) inscribe their own routes in an integrated-optics system; attractive, repulsive and even orbiting interactions of self-trapped beams could modulate/transfer/split/amplify light signals. Previous studies were restricted to certain types of media - nonlinear optical (NLO) materials - which respond to light under an extremely narrow range of conditions. Our research moves away from NLO materials and examines self-trapping phenomena in simple photochemical systems; these provide a much broader range of conditions for self-trapping studies. This research promises new insight and even entirely new forms of self-trapping phenomena. (ii) Structures with microperiodic modulations in refractive index can possess bandgaps for visible energies; light at wavelengths in the bandgaps can be tightly trapped, reflected and guided through defects in the lattice. Previous research focused on all-dielectric photonic crystals; theoretical studies predict that metallo-dielectric structures possess greatly-enhanced bandgaps but such structures are difficult to construct with conventional techniques. Our research develops metallo-dielectric polymer composites to construct metallo-dielectric periodic structures through simple, one-step lithographic processes. We also examine iridescent natural periodic structures - including ammonite cephalopod fossils. Understanding the sophisticated structural and optical properties of these 70-million year old fossils may provide insight for the design of synthetic photonic crystals.