Dark optical lattice

Hemmerich, A., Weidemiiller, M., Esshnger, T., Zimmermann, C., and Hansch, T. (1995). Trapping atoms in a dark optical lattice. Physical Review Letters, 75,... 

Grimm, R., Weidemiiller, M., and Ovchinnikov, Yu. B. (2000). Optical dipole traps for neutral atoms. In Advances in atomic, molecular, and optical physics (ed. B. Bederson and H. Walther), vol. 42, pp. 95-170. Academic Press, San Diego. Grynberg, G., and Courtois, J. (1994). Proposal for a magneto-optical lattice for trapping atoms in nearly-dark states. Europhysics Letters, 27, 41-46. 

In long-afterglow phosphors, optical excitation energy is stored in the lattice by trapping photoexcited charge carriers. The most prominent example is SrAl204 Eu,Dy after optical excitation of Eu, Eu is oxidized to Eu and Dy is reduced to Dy. Thermal excitation of Dy to Dy, followed by capture of the electron by Eu and subsequent Eu emission results in time-delayed Eu emission. The thermal excitation process of Dy determines the time delay. This particular material still generates visible emission after several hours in the dark. 

FIGURE 1.8 In (a) is an arbitrary set of points that might represent the atoms in a molecule, and in (b) is the optical diffraction pattern of that set of points. It is a continuum of light and dark over the whole surface of the screen. The mask (object) in the optical diffraction experiment in (c) is the periodic arrangement of the fundamental set of points in (a) in two dimensions (i.e., the repetition of the object according to the instruction of a lattice). The diffraction pattern of (c) is shown in (d). We would find that if we superimpose the point array in (d) upon the continuous transform in ( >), the intensity at each lattice point in (d) corresponds to the value of the continuous transform beneath. That is, the diffraction pattern in (d) samples the continuous transform in (b) at specific points determined by the periodic lattice of (c). 

Fig. 6.13. Optical and electron-microscopic micrographs of PpPTA fibers showing various features of the morphology, (a) ED-pattern (b) lattice image of the 110 planes (c) TEM-dark field image of the pleats, (d) SEM-image of filament cross-section, diameter 12 fim (e) peel morphology showing pleats (f) fracture morphology. Arrow indicates fiber axis. ...

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