A study of wire‐grid polarizers for projection displays

Abstract— The appropriateness of using wire‐grid polarizers (WGP) in projection displays is studied. In particular, we shall discuss the case of projectors with reflective light valves. We shall show that WGPs offer some distinct advantages over conventional polarizers, in terms of large extinction ratios and large numerical apertures. However, there is considerable light absorption leading to reduced light utilization efficiency. We also show that of the four possible combinations of configurations, only one offers the best contrast and efficiency.     

Designing multilayered wire‐grid polarizers using a monochromatic recursive convolution finite‐difference time‐domain algorithm

Multilayered wire‐grid polarizers (WGP) find application as low‐reflection polarizers in projection‐type liquid crystal display devices. A multilayered WGP is formed by adding thin layers on top of the metal ridges of an ordinary WGP. The ordinary WGP consists of a periodic array of parallel metal ridges, where the period of the array and the width of any individual metal ridge are typically less than the wavelength of the incident light. Such WGPs are often used as efficient polarizers. However, in certain applications, it is important to reduce the reflection from the WGP while preserving the polarization efficiency. One of the ways to achieve this goal is to add thin layers on top of the metal ridges of the ordinary WGP. The reduction in reflection from the multilayered WGP depends on the number and material of these additional layers. In this paper, we describe a design method for multilayered WGPs based on an effective medium theory, thin‐film computation method and a monochromatic recursive convolution finite‐difference time‐domain algorithm. The goal of design process is to identify suitable materials and thicknesses for the additional thin layers needed to lower the reflection appreciably. The design method is explained with the help of bilayered WGPs.     

Spectral‐polarizing properties and light stability of film polarizers with azodyes

Abstract— Results of the investigation of film polarizers on a base of polyvinyl alcohol and azobenzeneazonaphtalene dyes are presented. The dependence of the light stability of these polarizers on the structure and concentration of a dye, the stretching and conditions of the chemical treatment of films, as well as the physical state of the polymer matrix have been studied. Based on obtained results, a method for improving the light stability has been proposed.     

Optimization of bi‐layered nano‐wire grids as high‐efficiency polarizers for power recycling in liquid‐crystal displays

Abstract— Bi‐layered Al nano‐wire grids (N WGs) are proposed as high‐efficiency polarizers for power recycling in liquid‐crystal displays (LCDs). In comparison with single‐layered NWGs, the bi‐layered scheme is more cost‐effective with both less and more controllable fabrication steps. Two types of 150‐nm‐period NWGs with different cross sections were characterized and theoretically analyzed. A TM transmittance of over 66% and a contrast ratio as high as 8000 in the visible range were calculated. Furthermore, 5–8% increase in TM transmittance and an almost 20% enhancement in contrast ratio are achievable. The NWG sheet with a large contrast ratio as well as a high optical throughput acts as a reflective polarizer in the power‐recycling system of LCD backlight units. A total transmittance of above 70% in the visible region is predicted for the power‐recycling process, which is at least 9% higher in total light efficiency than the claimed result of commercial dual brightness‐enhancement film (DBEF).     

The role of LiF buffer layer in tris‐(8‐hydroxyquinoline) aluminum‐based organic light‐emitting devices with Mg:Ag cathode

Abstract— The device characteristics of organic light‐emitting devices based on tris‐(8‐hydroxyqunoline) aluminum with a thin layer of LiF inserted at the ITO and organic interface or organic and Mg:Ag cathode interface were investigated. A thin layer of LiF can enhance the electron injection when it was inserted only between the organic electron‐transporting layer and the Mg:Ag alloy cathode, but can block hole injection when inserted between the ITO anode and the organic hole‐transport layer. By inserting both a 1.0‐nm LiF layer at side of the ITO anode and a 0.5‐nm LiF layer under the Mg:Ag cathode, the device, at a current injection of 10 mA/cm², exhibited the highest current efficiency of 8.2 cd/A and power efficiency of 1.93 lm/W for all the types of devices investigated in this study. Both the current efficiency and power efficiency of the device were improved by 1.2 times at a current injection of 10 mA/cm², compared to the standard device without any LiF buffer layer. This is due to the increased electron injection and decreased hole injection that off‐sets the imbalance of electron and hole injection and brings it towards the balanced injection of electrons and holes, thus reducing the non‐productive hole current.