Lasing via a phase retardation defect mode is reported for the first time. The Figure shows the far‐field pattern of laser emission realized by inserting an anisotropic nematic liquid crystal (LC) defect layer between polymer cholesteric LC layers. The system mimics the cuticle of Plusiotis resplendens, a beetle, using the birefringence of the anisotropic layer to achieve reflectance greater than the 50 % provided by simple cholesteric LC photonic bandgaps.

Lasing conditions in a dye-doped cholesteric liquid crystal ͑ChLC͒ have been studied in view of optical modes for the light propagating in ChLCs using a polymeric dye with the transition dipole moment parallel to the local director of the ChLC host. We found that lasing always occurs at the lower-energy edge of the photonic gap. This is because that the optical eigen mode at the lower-energy gap is linearly polarized parallel to the director, while it is perpendicular at the higher-energy gap. Because of this well-defined lasing condition, low-threshold lasing was successfully achieved.

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We review recent experimental and theoretical work aimed to understand the reaction dynamics of hydrogen molecules at metal surfaces. Diffraction experiments and calculations using ab initio determined six-dimensional potential energy surfaces were carried out on several single-crystal surfaces: NiAl(110), Pt(111), Pd(111) and Pd(110). We discuss the general trends observed in the energy range studied (20-150 meV) when going from nonreactive to very reactive surfaces as well as specific features of the dynamics which can be seen in diffraction studies.