In this paper, a single-layer circular polarizer for linear polarized horn antenna is proposed. The multiple reflected waves between the aperture and array provide desired phase differences between vertical and horizontal polarizations. The measured gain of the fabricated antenna is 14.4 dBic and the half power beamwidths of the vertical polarization are 28 and 24 deg. and those of the horizontal polarization are 31 and 23 degrees in the vertical and horizontal planes. The polarizer has a low impact on the gain and beamwidth of the primary horn antenna and their changes are within 1.7 dB and 10 degrees. The 3 dB fractional bandwidth of the axial ratio is measured to be 1.4%.

This paper proposes an analytical method to design septum-type polarizers by assuming a polarizer as a series of four septum elements with a short ridge-waveguide approximation. We determine parameters of respective elements in such a manner that, at the center frequency, the reflection coefficient of the first element is equal to that of the second one, the reflection of the third one equals to that of the forth, and the electrical lengths of the first, second and third elements are 90 deg. We name this method the Short Ridge-waveguide Approximation Method (SRAM). We fabricated an X-band polarizer, which achieves a cross polarization discrimination (XPD) value of 40.7-64.1 dB over 8.0-8.4 GHz, without any numerical optimization.

We show that light leakage that occurs in reflective polarizers at large angles of incidence can be suppressed by using anisotropic dielectric multilayers with larger reflective indices in thickness direction and that the interference-included 2×2 Jones matrix method is useful for the investigation of the optical propagation properties of the dielectric multilayers. The thickness of the reflective polarizer can also be reduced by optimizing the distribution of the multilayers in the stack, whilst considering the visual sensitivity. These results indicate that it is possible to realize a high-quality liquid crystal display with wide viewing angles and high light utilization efficiency.

Graphene is attracting attention in electrical and optical research fields recently. We measured the optical absorption characteristics and polarization dependence of single-layer graphene (SLG) on sub-micrometer Si waveguide. The results for graphene lengths ranging from 2.5 to 200 $mu$ m reveal that the optical absorption by graphene is 0.09 dB/$mu$ m with the TE mode and 0.05 dB/$mu$ m with the TM mode. The absorption in the TE mode is 1.8 times higher than that in the TM mode. An optical spectrum, theoretical analysis and Raman spectrum indicate that surface-plasmon polaritons in graphene support TM mode light propagation.

A composite patch array antenna with built-in polarizer has been developed to reduce road clutter noise by 20 dB for 76 GHz automotive radars. A polarizer is placed in front of Tx and Rx patch arrays within their reactive near-field region to suppress cross-polarized sidelobe radiation from their feeding lines while maintaining a low-profile characteristic with 4 mm thickness. Additional metal-lined absorbers within the composite antenna structure, while terminating cross-polarized waves undesirably excited by the patch arrays, also serve as miniature clutter plates to further reduce sidelobes toward the road surface. The resultant composite antenna achieved sidelobe levels of -45 dB, a 20 dB improvement over standard patch arrays, at elevation angles close to 90.

We experimentally demonstrated polarization-mode dispersion (PMD) compensation by distributing polarizers with only 1 degree of freedom (DOF) along the transmission line. The average power penalty was measured to be 0.4 dB by inserting four compensators, where average differential group delay was 47% of bit period.

The operation of a polarization mode dispersion (PMD) compensator using a polarizer and a Faraday rotator-based polarization controller (FRPC) is analyzed in detail, and the compensation performance is experimentally evaluated in 40 Gbit/s operation. The evaluation results show that a wide range of differential group delay over a bit period can almost be completely compensated using the PMD compensator. The characteristics of electrical spectrum-based signal monitoring methods are investigated in detail, and the results shows advantages of a low frequency band monitoring method that produces about double the wider dynamic range than a fundamental repetition frequency monitoring method. The automated PMD compensator using a polarizer and a FRPC driven by the low frequency band monitoring method is experimentally investigated using a terrestrial 40 Gbit/s wavelength division multiplexing system involving 350-km installed single-mode fibers. The PMD compensator produces highly stable signal performance in the field environment for a long term and reduces the standard deviation of the Q-factor distribution.

Autocloning is a method for fabricating multi-dimensional structures by stacking the corrugated films while keeping the shape. Its productivity, robustness against perturbation, and flexibility regarding materials and lattice types make autocloning suitable for mass production of photonic crystals. Therefore we aim to industrialize autocloned photonic crystals. Recently, we are starting to market polarization beam splitters for optical telecommunication by using 2D photonic crystals, and are developing some devices using the splitters, such as isolators or beam combiners. The applications of the splitters are also extending to multi-section type of devices and to visible range devices. Meanwhile, development of optical integrated circuits by utilizing autocloned photonic crystals is in progress. Low loss propagation and some functions have been demonstrated.

Feasibility of a color shutter using ferroelectric liquid crystal polymer panel and a field sequential ultra high-resolution CRT with the color shutter as a color field-switching device was studied. The color shutter consists of ferroelectric liquid crystal polymer panels and color polarizers. First, evaluation indices of the color shutter, such as the color gamut, the average transmittance and the white chromaticity shift, were formulated, and the simulation of evaluation indices was examined, where the spectral transmittance characteristics of the polarizer were changed in steps. It was indicated that there was a tradeoff between the color gamut and the average transmittance of the color shutter, and the shutter configuration that provides 0.096 (63% to NTSC) color gamut and 4.3% average transmittance was selected based on the simulation results. Next, the three-line simultaneous scanning method of the monochrome CRT was improved so that the disturbance due to the raster modulation was eliminated by averaging the distribution of beam luminance apparently. To confirm results of the study, the prototype of 21-inch screen size was produced, and the following display characteristics was obtained: luminance of 71 cd/m2, contrast ratio of 146:1 and color gamut of 0.096 (63% to NTSC) under the standard room lighting environment.

The optical characteristics of the fiber loop polarizer are investigated considering the birefringence in the fiber loop. The experimental and the theoretical spectrum transmissions agree well with each other. The extinction ratio and the insertion loss of the fiber polarizers have been improved for practical use.