Saravnamuttu Research Group McMaster University | Inspiring Innovation and Discovery

Optochemical Organization

Optochemical organization is a route developed in our group to 2-D, 3-D optical and microstructural lattices that marries the elegant spontaneity of self-organisation to the precision and directionality of directed-beam lithography. Resulting microstructures are composed of multimode, multi-wavelength cylindrical polymer waveguides. Our technique relies on the inherent instability, modulation instability of a broad, uniform incandescent beam. By imposing controlled noise on the beam, filaments can be coaxed into a diverse collection of 2-D, 3-D lattices with square, near-cubic, cubic, BCC and woodpile symmetries as well as lattices comprising both black and bright channels.

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A 3-D lattice of white light: optochemical organization of a near-cubic lattice of self-trapped filaments (Burgess, Ponte et al)

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An optochemically organized polymer waveguide lattice with near cubic symmetry (Burgess, Ponte et al)

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Optochemically organized lattice of bright and dark filaments

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Because light-induced changes in a photopolymer are typically irreversible, optical lattices formed in this way permanently inscribe the corresponding lattice of waveguides. Optochemical organisation is therefore a rapid (seconds to minutes-long), single-step, room temperature route to dense 2-D, 3-D lattices comprising tens of thousands of cylindrical waveguides – such structures would be extremely challenging to construct through conventional lithographic processes. Our technique does not require lasers but instead employs incoherent light emitted by inexpensive incandescent lamps. The resulting structures have potential applications as dense optical interconnect arrays, nonlinear photonic lattices, which are the next generation of photonic crystals, light-collecting and light-directing coatings.

A generalized light-based pathway to functional optical materials

Our aim is to establish optochemical organisation as a robust, general tool to generate a library of 2-D, 3-D lattices with unique optical functionalities. To this end, we examine a diverse range of systems with strong characteristic optical responses (e.g. plasmon resonance, birefringence of liquid crystals, photo-induced isomerization). These include optochemically self-organized photopolymers doped with stable dispersions of metal nanoparticles. Resonance frequencies of metal nanoparticles are strongly influenced by their size, shape, composition, spatial distribution as well as their dielectric environment, for e.g., when embedded in dielectric photonic crystals, discrete metal particles give rise to enhanced band gaps. Optochemically organised metallodielectric lattices would provide opportunities to understand the effects of plasmon resonance on waveguide lattices. Another example is optochemical lattices composed of liquid crystalline channels or waveguides. Because of their ability to resolve polarised light, 3-D arrays of birefringent waveguides possess greater degrees of freedom in processing data-carrying light signals and could serve as biomimetic structures inspired by the stomatopod crustacean’s eye, which is sensitive to polarised light.