Low Refractive Materials Research Articles

Syntheses of Dumbbell-Shaped Trifluoropropyl-Substituted POSS Derivatives Linked by Simple Aliphatic Chains and Their Optical Transparent Thermoplastic Films.

Dumbbell-shaped trifluoropropyl-substituted C2-linked POSS (POSS-DE), C3-linked POSS (POSS-DP), and C6-linked POSS (POSS-DH) were prepared by corner-capping of hepta(3,3,3-trifluoropropyl)tricycloheptasiloxane trisodium silanolate (F7-Na) with 1,2-bis(trichlorosilyl)ethane, 1,3-bis(trichlorosilyl)propane, and 1,6-bis(trichlorosilyl)hexane, respectively. The structures of these obtained compounds were confirmed by 1H, 13C, and 29Si NMR spectra and MALDI–TOF–MS analysis. In the case of POSS-DP and POSS-DH, spin coating of hexafluorobenzene solutions and subsequent baking at 100 °C for 3 min gave optical transparent films. POSS-DE, however, formed opaque whitish films. Refractive indices of the transparent films were in the range of 1.38 to 1.39, which were the same as those of the corresponding random silsesquioxanes prepared by baking at 250 °C. POSS-DP and POSS-DH are regarded as low temperature processing low refractive materials. Thermal stabilities of the dumbbell-shaped POSS derivatives were higher than that of allylhepta(3,3,3-trifluoropropyl)-T8-silsesquioxane (POSS-F7A1). Both the glass transition and melting temperatures of the dumbbell-shaped POSS derivatives were observed by DSC analysis.

CaF2두께 변화에 따른 ZnS/CaF2/ZnS/Cu 다층 박막의 광특성

Layered ZnS/<TEX>$CaF_2$</TEX>/ZnS/Cu film was deposited on glass substrate by using evaporation method. ZnS and <TEX>$CaF_2$</TEX> were chosen as high and low refractive materials. Cu was used as mid-reflective layer. Reflectance with different optical thickness of <TEX>$CaF_2$</TEX> ranging from <TEX>$0.25{\lambda}\;to\;0.5{\lambda}$</TEX> were systematically investigated by using spectrophotometer. In order to expect the experimental results, the simulation program, the Essential Macleod Program(EMP) was adopted and compared with the experimental data. Based on the results taken by spectrophotometer, the ZnS/<TEX>$CaF_2$</TEX>/ZnS/Cu multi-layered thin film show the maximum reflectance of 80% at 625nm <TEX>$(0.25{\lambda}\;in\;CaF_2)$</TEX> and 42% at 660nm <TEX>$(0.5{\lambda}\;in\;CaF_2)$</TEX> respectively. As compared with the experimental results and simulation data, it was confirmed the experimental data is well matched with the EMP data.

Improvement of the sensitivity and spatial resolution of pixelated CsI:Tl scintillator with reflective coating

Abstract Pixelated-scintillator films used for X-ray image sensors were developed and tested. The air gap between scintillator pixels reduces the transport of visible light photons generated by X-rays into the neighboring pixels so it will maximize the overall spatial resolution as well as the light collection efficiency of an X-ray imager. For further improvement, the inter-pixel gaps and surface are filled and coated with a reflective or a lower refractive material than an CsI(Tl) scintillator. The scintillator films of 30–40 μm thickness were made with thallium-doped CsI by the conventional physical vapour deposition process on glass substrates with a photo resist layer patterned by UV lithography. In this work, the effects on light collection efficiency and spatial resolution of the pixelated-scintillator films before and after reflective coating were evaluated using a CCD sensor and X-rays within the medical diagnostic energy range.

�ber Fabry-Perot-Verspiegelungen aus dielektrischen Vielfachschichten f�r den Spektralbereich von 2350 bis 20000 �

The production and the performance of dielectric multilayer mirrors for Fabry-Perot interferometers from 20000 A to 2350 A are described. Details of the evaporation apparatus and techniques are given. The optical data — reflection factor, absorption factor and flatness — are represented graphically and discussed. For all wavelength cryolite served as low refractive material. The high refractive materials used were ZnS for wavelengths from the infrared to λ>4100 A, Sb2O3 for λ between 4200 A and 3200 A and PbF2 for the shorter wavelengths to λ=2350 A. For PbF2 an exciton-band at 2190 A has been found.