Scatterings
Magnets Control Photonic Crystals
Researchers at the University of California, Riverside, not only discovered a way to make photonic crystal structures that self-assemble; they also developed a simple method for actively altering the period of the crystals.
The color reflected from a solution of iron oxide nanoparticles can be tuned by changing the magnetic field. The reflection occurs because the particles self-assemble into a photonic crystal that refuses light at certain wavelengths. The period of the crystal is superparamagnetic.
Photonic crystals are a hot topic right now, with designs based on opal structures making news regularly (OPN, October 2007, p. 10). Creating structures with the right characteristics on a tiny scale is far from simple, however.
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