In support of a spaceborne astrophysics instrument design, we have studied high UV filter efficiency and strong transmission blocking out to the end of Si response at 1100nm. For filters at wavelengths 297.5nm/338.5nm/379.5nm, these attributes are achieved with the combination of hard sputtered dielectric coatings on colored glass substrates. The filterglass substrates can be used to suppress ghost images caused by reflection at the exit face which is a common problem of all interference filter designs. Known disadvantages of filterglasses like solarization or autofluorescence are discussed and possible ways to mitigate are discussed. At two shorter wavelengths, 215.5nm and 256.5nm, metaldielectric Fabry-Perot stacks are applied on fused silica. Those traditional designs are advantageous due to their efficient blocking up to the mid IR range and economic low number of layers. We discuss the different design possibilities of metal-dielectric filters and ways to improve the steepness of the slopes. Resulting spectra are expressed.
The chromophore orientation distribution in photoaddressable bis-azo copolymer thin films is investigated as a function of the poling temperature and the chromophore concentration. The first, second, and third order parameters are deduced from the linear electro-optic coefficients and the linear dichroism by free-beam interferometry and angle-resolved spectroscopy, respectively. Absorption spectra obtained by density-functional calculations are compared with the experimentally observed ones and support the picture of differently aligned bis-azo dye molecules in a trans,trans-configuration. The various kinds of ordering in samples poled at different temperatures is confirmed by complementary wide-angle X-ray scattering. Furthermore, we show that a higher thermal stability for applications can be reached by fractionating the polymer, and how such a material can be successfully employed to build a large-area Fabry-Perot-Modulator using the electro-optic effect.
Investigating dynamics in a disordered solid material below, at, and well above glass transition temperature, we show that (1) to describe glass dynamics entirely it has to be regarded over a long
range on logarithmic time scale, (2) a single stretched exponential function (Kohlrausch-Williams-Watts) can never describe the data, (3) stretching exponents do not cover the ranges previously suggested (from 0 to 1, e.g. as a sigmoid function). Optically recorded dynamics (measured by ellipsometry) is brought into connection with dielectric spectroscopy.
The relaxational response of a photorefractive polymer subjected to different poling voltages slightly above the glass transition temperature is measured using ellipsometry. We discuss our results using a new curve-fit function, which provides a good description of the experimental data. Using this new function we examine how the poling voltage influence the poling behavior of the chromophores. Furthermore, it is shown that the characteristic time for turn-off behavior is strongly influenced by the time span elapsed since turn-on.
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