Photonic band structure of cholesteric elastomers.

We calculate the photonic band structure along and oblique to the helix axis of cholesteric elastomers. They are highly deformable, self-assembling systems. They display brilliantly colored reflections and lasing owing to stop bands in their photonic band structure. This band structure varies sensitively and extensively with strain. We show how additional stop bands open up and how they all shift in frequency. We predict a "total" stop band, that is, for both circular polarizations and show analytically how stop bands scale with strain. The extension of stop bands to a range of angles thereby creates pseudogaps, and the relevance to low-threshold lasing is discussed.