Applied Physics

Light amid Disorder

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Science  08 Feb 2008:
Vol. 319, Issue 5864, pp. 699
DOI: 10.1126/science.319.5864.699c

In semiconductors, the concept of an energy gap that separates conducting electrons from localized valence states is fundamental to understanding the materials' optical and electronic properties. Researchers discovered in the 1980s that photons can behave in a similar way: Optical materials fabricated with just the right periodic structures exhibit energy (or frequency) regions where light passes through and other energy zones where transmission of light is blocked. Just as semiconductor band gaps lead to a wide range of useful technological properties, photonic band gaps can do the same for optical materials. Researchers have assumed that in order to produce the photonic band gaps, high-quality crystalline materials are required. Edagawa et al. present computational results showing that amorphous diamond without lattice periodicity can also exhibit strong photonic band gaps. The results challenge the traditional view that photonic band gaps are strictly a consequence of Bragg reflection and interference in which electromagnetic waves are scattered from various planes formed by a periodic atomic lattice. Thus, a range of photonic band gap systems could potentially be synthesized from materials such as polymers, proteins, and colloids that lend themselves naturally to amorphous structures. — DV

Phys. Rev. Lett. 100, 13901 (2008).

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