The inorganic polarization devices for visible range, namely the absorptive gird polarizers and form birefringent wave plates, were developed. These devices are composed only of inorganic materials and glancing angle deposition technique was employed to fabricate their optical functional layers, which are the absorptive layer and columnar birefringent structure for the polarizers and wave plates, respectively. The optical performance and reliability of these devices were experimentally evaluated and showed them to be suitable for applications requiring high light resistance and thermal durability, such as liquid crystal display projectors.
We investigated the optical characteristics and microstructures of wave plates composed of Ta2O5(100−x)+TiO2(x) and prepared by the so-called serial bideposition technique. While a single-layer film prepared by conventional oblique deposition technique has a tilted columnar structure (i.e., tilted optical axis), a serial bideposition film has a narrow, long columnar structure; this ensures that the optical axis of the film is along the quasinormal to the substrate, thus reducing haze. The influence of using additives with Ta2O5 was investigated as well. It was found that additive TiO2 improves optical transmittance at shorter wavelengths. For verifying the advantage of this type of wave plates, quarter wave plates with optimized TiO2 content were fabricated and their optical performance and reliability were evaluated against those of organic-type wave plates. The results show that the inorganic wave plate prepared by serial bideposition is advantageous for applications where high-transmittance and high-temperature durability are essential.
We have examined antireflection (AR) coatings for high reflectivity metals such as Al on the basis of the admittance diagram. The proposed AR coatings consist of bilayers of absorptive and dielectric materials. A wide variety of materials can be used for AR coatings by tuning the thicknesses of both the absorptive and the dielectric layers. The bilayered AR concept has been applied to reduce the reflectance of wire grid (WG) polarizers made of Al. An absorptive FeSi 2 layer has been deposited by the glancing angle deposition technique immediately on the top of Al wires covered with a thin SiO 2 layer. For the optimum combination of the thicknesses of FeSi 2 and SiO 2, the reflectance reduces to lower than a few percent independent of the polarization, whereas the transmission polarization properties remain favorable. We have demonstrated that Ge is also appropriate for the low-reflectivity WG polarizers as an absorptive material. Because low-reflectivity WG polarizers are completely composed of inorganic materials, they are useful for applications requiring thermal durability, such as liquid crystal projection displays.
We theoretically propose two types of antireflection (AR) coatings for metals. One type consists of a single
layer of a dielectric material having a high refractive index. The other type consists of bilayers of absorptive
and dielectric materials that are used in order to reduce the reflectance of high reflectivity metals such as Al
in the visible region. The bilayered AR concept has been applied to reduce the reflectance of wire grid (WG)
polarizers made of Al. An FeSi2 layer, which serves as an absorptive layer, has been deposited by the glancing
angle deposition technique immediately on the top of Al wires covered with a thin SiO2 layer, which serves
as a gap layer. For the optimum combination of the thicknesses of FeSi2 and SiO2, the reflectance reduces
to lower than a few percent independent of the polarization, whereas the transmission polarization properties
remain favorable. Because low reflectivity WG polarizers are completely composed of inorganic materials, they
are useful for applications requiring thermal durability, such as liquid crystal projection displays.
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