Metal Wire Grid Polarizer Research Articles

Fabricating insertion structures for metallic wire grid polarizers by nanoimprint and CMP process

This paper proposed an efficient process, with high throughput, for manufacturing stable insertion structures inside PMMA substrates through only three steps, i.e., nanoimprint, metal deposition and chemical mechanical polishing (CMP). The insertion structures with potential applications in metallic wire grid polarizers possesses the advantages of being able to avoid the embedded nanostructure from damage due to contamination or stresses during packaging process or transportation. Furthermore, this architecture offers a flatly finished surface to facilitate subsequent processes, such as sealing and packaging in backlight module for LCD. In this paper, the Al wire gratings of the insertion structure with 100nm in linewidth, 240nm in pitch and 235nm in height were successfully replicated into the PMMA substrate of 1cm2. AFM and FE-SEM were utilized to observe the imprinted surface, and the results indicated that the embedded nanostructure underneath a flatly finished surface was obtained. In addition, the extinction ratio of the fabricated device is over 171.8 with high transmittance of 91.6% at a wavelength of 650nm of incident light.

Liquid-crystal micropolarimeter array for full Stokes polarization imaging in visible spectrum

In this paper, we describe the design, modeling, fabrication, and optical characterization of the first micropolarimeter array enabling full Stokes polarization imaging in visible spectrum. The proposed micropolarimeter is fabricated by patterning a liquid-crystal (LC) layer on top of a visible-regime metal-wire-grid polarizer (MWGP) using ultraviolet sensitive sulfonic-dye-1 as the LC photoalignment material. This arrangement enables the formation of either micrometer-scale LC polarization rotators, neutral density filters or quarter wavelength retarders. These elements are in turn exploited to acquire all components of the Stokes vector, which describes all possible polarization states of light. Reported major principal transmittance of 75% and extinction ratio of 1100 demonstrate that the MWGP's superior optical characteristics are retained. The proposed liquidcrystal micropolarimeter array can be integrated on top of a complementary metal-oxide-semiconductor (CMOS) image sensor for real-time full Stokes polarization imaging.

Feasibility study on twisted nematic liquid-crystal cell with two cross-embedded wire-grid polarizers as alignment and electrode for projection displays

For this study, twisted nematic liquid crystals (TN-LCs) are sandwiched between two cross-embedded wire-grid polarizers (WGPs) as alignment and electrodes for projection displays. In the proposed device, the WGPs replace not only the sheet polarizers in a conventional TN-LC cell, but also the front and rear alignment layers and transparent electrodes. It is found that the structure of a WGP microgroove is suitable for alignment; however, the proposed TN-LC cell exhibits a multidomain phenomenon because there is no apparent pretilt angle on the two WGPs. The multidomain phenomenon can be solved by the annealing method and by blending chiral material with the TN-LC for twisting the LC in the same direction. In addition, the surface resistance of the aluminum WGP is two orders lower than the indium-tin-oxide glass substrates, so that it is suitable for electric conductivity and for use as a transparent electrode. Also, metallic WGPs exhibit a higher heat resistance characteristic than plastic sheet polarizers, making them robust. As a result, the threshold voltages, the saturation voltages, and the response time of the proposed TN-LC cell are almost identical to the conventional TN-LC cell. The contrast ratio of the LCD projector with the proposed TN-LC cell and the quarter-wave plate exhibit the best characteristics in comparisons with the other LCD projectors. Thus, the proposed TN-LC cell represents a simple and feasible solution for the next generation of high-brightness projection display devices.

Large‐Area Dual‐Scale Metal Transfer by Adhesive Force

We report a large-area, dual-scale metal transfer method by using a difference in adhesive force. Rigiflex polyurethane acrylate (PUA) molds with engraved nanoscale patterns were used to transfer metal layers (Au or Al) to flexible polyethylene terephthalate (PET) substrate. Transfer process was performed sequentially for the metal layers on ridge and valley regions of the mold, resulting in a dual-scale metal transfer from a single master. A simple metal wire grid polarizer was fabricated and analyzed using this method.

Bilayer metal wire-grid polarizer fabricated by roll-to-roll nanoimprint lithography on flexible plastic substrate

The bilayer metal wire-grid polarizer has several advantages over single-layer wire-grid polarizer and conventional polarizer since it provides higher polarization efficiency and can be easily fabricated. In this work, the authors demonstrate the fabrication of bilayer metal wire-grid polarizer on flexible plastic substrate by a continuous roll-to-roll nanoimprint lithography (R2RNIL) process and evaluate its performance. To fabricate wire-grid polarizer, subwavelength grating structure in epoxysilicone material is first created on a flexible PET substrate by UV R2RNIL followed by aluminum deposition. In initial measurement, extinction ratio exceeding 1000 has been achieved.