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.

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.

We have studied the lasing characteristics from a dye-doped nematic layer sandwiched by two polymeric cholesteric liquid crystal (PCLC) films as photonic band gap materials. The nematic layer possessing birefringence brings about the following remarkable optical characteristics; (1) reflectance in the photonic band gap (PBG) region exceeds 50 % due to the retardation effect, being unpredictable from a single CLC film, (2) efficient lasing occurs either at the notch of PBG or at the photonic band edge, (3) the lasing emissions contain both right-and left-circular polarizations, and (4) tunable lasing can be achieved by the reorientation ofnematic liquid crystal molecules under the application ofan electric field.

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