Materials Science

Spiral Photonic Crystals

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Science  18 Mar 2005:
Vol. 307, Issue 5716, pp. 1693
DOI: 10.1126/science.307.5716.1693a

Photonic crystals are periodic dielectric structures that have a band gap that stops the propagation of a certain frequency range of light. Through the inclusion of defects or cavities, photonic crystals can be designed to trap or guide light and are thus of considerable interest for use in optics and communications. Three-dimensional photonic crystals have been designed from theory, but most have a complex structure that cannot be fabricated using traditional layer-by-layer approaches. Seet et al.use direct laser writing to fabricate circular and square spiral architecture structures. The process works through the curing or hardening of a polymeric photoresist as it absorbs multiple photons from a tightly focused laser beam. In previous systems, a liquid photoresist has been used, but because of shrinkage that occurs on curing, this method limits the resolution that can be obtained. The photoresist SU-8, by contrast, is solid both before and after processing and undergoes only small refractive index and density changes upon curing, making the writing process more uniform. Because of the self-supporting nature of the material, complex defect structures could be engineered into the periodic crystals. — MSL

Adv. Mater. 17, 541 (2005).

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