Optochemical Organization in a Spatially Modulated Incandescent Field: A Single-Step Route to Black and Bright Polymer Lattices
mediaposted on 29.01.2013, 00:00 by Kailash Kasala, Kalaichelvi Saravanamuttu
We report that incandescent beams patterned with amplitude depressions (dips) suffer instability in a photopolymerizable system and organize into lattices of black and bright self-trapped beams propagating respectively, through self-induced black and bright waveguides. Such optochemically organized lattices emerge when beams embedded with a hexagonal or square array of dips initiate free-radical polymerization and corresponding changes in refractive index (Δn) along their propagation paths. Under these nonlinear conditions, the dips evolve into a hexagonal or square lattice of black beams, while their bright interstitial regions become unstable and divide spontaneously into multiple filaments of light. These filaments have a characteristic diameter (df) and organize into a variety of geometries, which are determined by the shape and dimensions of the bright interstices. At interstitial widths > 2df, filaments are randomly positioned in space, whereas at widths < 2df, the interstices are occupied by a single file of filaments encircling each dark channel. When the interstitial width ≈ df, the filaments organize into lattices with long-range hexagonal or square symmetry. By employing anisotropic interstices such as rectangles, filamentation can be selectively elicited along the long axis, leading to a lattice of filament doublets. This work demonstrates the versatility and significant potential of optochemical organization to generate complex, optically functional polymer lattices, which cannot be constructed through conventional lithography or self-assembly. Specifically, the study introduces a new generation of waveguide lattices, in which light propagation is co-operatively managed by black and bright waveguides; the former suppress local light propagation and, in this way, enhance light confinement and guidance in proximal bright waveguides.