Circular Polarization Filters Research Articles

Soft x-ray circular polarizer using magnetic circular dichroism at the Fe L3 line

Linearly polarized soft x-rays are converted to elliptical polarization at the Fe L3 line (707 eV) using magnetic circular dichroism (MCD) on transmission through thin Fe films. A linear polarizer measured the transmitted polarization at different incidence angles to vary as expected from a model for in-plane magnetization, and also to exhibit a weak MCD effect at normal incidence interpreted to originate from perpendicular interface anisotropy. An MCD signal from a downstream Fe film was produced by switching the helicity of x-rays transmitted through an upstream circular polarizer. Practical considerations for optimizing the production of circular polarization are discussed, and synchrotron radiation applications using these circular polarizing filters are suggested.

Contrast enhancement of LED, vaccum fluorescent and plasma displays with circular polarizing filters

Filters are widely used for contrast enhancement of active electronic displays. This paper considers the application of circular polarizers to LED, vacuum fluorescent and plasma displays under a variety of ambient illumination situations. Relevant parameters controlling contrast enhancement have been identified. The degree of contrast enhancement obtained with appropriate circular polarizing filters under different ambient illumination values is reported for each display type. These values are compared with those obtained using non-polarizing chromatic filters. In general, when contrast is being degraded by specular reflections of ambient light, the circular polarizing filters improve contrast to a much greater extent than the non-polarizing filters.

Measurement of contrast enhancement in VDU screens

Contrast enhancement has been measured on three different VDUs with each of four different enhancement filters. The contrast enhancement filters are of different types — circular polarizing, mesh, neutral isotropically absorbing, and spectrally selective isotropic absorbing. For situations where the contrast reduction is caused by near-specular reflection of ambient light, the circular polarizing filter is considerably more effective than the others. For situations where the contrast reduction is caused by non-specular reflection of ambient light, the filters were all about equally effective. Thus, in an average situation where contrast of the unfiltered VDU image is reduced by both near-specular and non-specular reflections, it would be expected that the circular polarizer would enhance contrast to a noticeably greater extent than the other filters. Resolution was also measured through each of the filters which had been tested for contrast enhancement. The mesh filter noticeably degraded resolution, whereas the circular polarizer and the isotropically absorbing filters did not.

A Quasioptical Circuit Technology for Shorttillimeter-Wavelength Multiplexer

This paper describes constructions and electrical performances of shortmillimeter-wavelength quasioptical passive circuits using the Gaussian beam mode, i.e., beam mode Iaunchers, polarization-independent beam splitters, circular polarization duplexers, filters, diplexers, and multiplexer. The diplexers were devised to handle wide bandwidths with fairly low loss and to have a sharp cutoff response so that they can be applied to telecommunications systems. Experiments on these components including frequency multiplexers and antenna feed systems were carried out in the 100-GHz band. It is shown that quasioptical circuits are particular useful in reducing insertion loss of multiplexing systems for shortmillimeter wavelengths.