Dick K. G. de Boer

Wire-grid diffraction gratings used as polarizing beam splitter for visible light and applied in liquid crystal on silicon

The application of wire grid polarizers as efficient polarizing beam splitters for visible light is studied. The large differences between the transmissivity for different polarizations are explained qualitatively by using the theory of metallic wave guides. The results of rigorous calculations obtained by using the finite element method are compared with experiments for both classical and conical mount. Furthermore the application of wire-grid polarizers in liquid crystal on silicon display systems is considered.

Application of genetic algorithms for characterization of thin layered materials by glancing incidence X-ray reflectometry

A genetic algorithm for characterization of thin-layered materials by glancing incidence X-ray reflectometry is proposed. For both simulated and measured data good fits are obtained within a single run. This reduces the amount of human effort and expertise necessary for analyzing reflectivity measurements which makes genetic algorithms an attractive alternative to methods currently used.

2-D/3-D displays based on switchable lenticulars

— An attractive concept for 3-D displays is the one based on LCDs equipped with lenticular lenses. This enables autostereoscopic multiview 3-D displays without a loss in brightness. A general issue in multiview 3-D displays is their relatively low spatial resolution because the pixels are divided among the different views. To overcome this problem, we have developed switchable displays, using liquid-crystal (LC) filled switchable lenticulars. In this way, it is possible to have a high-brightness 3-D display capable of fully exploiting the native 2-D resolution of the underlying LCD. The feasibility of LC-filled switchable lenticulars was shown in several applications. For applications in which it is advantageous to be able to display 3-D and 2-D content simultaneously, a 42-in. locally switchable prototype having a matrix electrode structure was developed. These displays were realized using cylindrically shaped lenticular lenses in contact with LC. An alternative for these are lenticulars based on gradient-index (GRIN) LC lenses. Preliminary results for such switchable GRIN lenses are presented as well.

Progress in phosphors and filters for luminescent solar concentrators

Luminescent solar concentrators would allow for high concentration if losses by reabsorption and escape could be minimized. We introduce a phosphor with close-to-optimal luminescent properties and hardly any reabsorption. A problem for use in a luminescent concentrator is the large scattering of this material; we discuss possible solutions for this. Furthermore, the use of broad-band cholesteric filters to prevent escape of luminescent radiation from this phosphor is investigated both experimentally and using simulations. Simulations are also used to predict the ultimate performance of luminescent concentrators.

Total reflection X-ray fluorescence of single and multiple thin-layer samples

Abstract In Total-reflection X-Ray Fluorescence (TXRF) the penetration depth of the exciting X-rays can be varied between a few nanometers and a few micrometers. In this paper the extension of the application of this technique to thin-film analysis is studied. First a theory is described with which the angular dependence of TXRF intensities can be calculated. Next calculated data are shown for various thin-film samples. The theoretical results compare favourably with preliminary experiments performed with a modified diffractrometer equipped with an energy-dispersive X-ray detector. The conclusion is that TXRF, especially when combined with X-ray reflectivity measurements, is a promising technique to obtain information about quantity and distribution of material over the various layers. The expected detection limits for this case are of the order of 10 13 atoms cm −2 .

Short period holographic structures for backlight display applications.

The use of holographic structures is promising for the realization of efficient systems in backlight applications for displays. By applying surface relief gratings on top of a side-lit lightguide we realize a backlight that avoids the use of color filters. The grating is used as a light outcoupling and color-separating element. The demands for this grating are stringent and calculations have been performed to meet them. A prototype backlight, including the grating structure, has been assembled and characterized. Results of experiments are discussed.

General polarized ray-tracing method for inhomogeneous uniaxially anisotropic media

Uniaxial optical anisotropy in the geometrical-optics approach is a classical problem, and most of the theory has been known for at least fifty years. Although the subject appears frequently in the literature, wave propagation through inhomogeneous anisotropic media is rarely addressed. The rapid advances in liquid-crystal lenses call for a good overview of the theory on wave propagation via anisotropic media. Therefore, we present a novel polarized ray-tracing method, which can be applied to anisotropic optical systems that contain inhomogeneous liquid crystals. We describe the propagation of rays in the bulk material of inhomogeneous anisotropic media in three dimensions. In addition, we discuss ray refraction, ray reflection, and energy transfer at, in general, curved anisotropic interfaces with arbitrary orientation and/or arbitrary anisotropic properties. The method presented is a clear outline of how to assess the optical properties of uniaxially anisotropic media.

Ellipsoid X-ray focussing for synchrotron-radiation microprobe analysis at the SRS, Daresbury, UK

Abstract A focussing monochromator for synchrotron-radiation microprobe analysis has been made by bending and fixation of a Si(111) crystal onto an ellipsoidal mould produced by numerically controlled diamond cutting. Experiments were performed using 15 keV radiation from the SRS dipole line. Measured beam profiles, topograms and fluxes are compared with the results of a ray-tracing program. In the experiment the spot size has been reduced, if compared with a flat monochromator, by a factor of 1000 horizontally and by a factor of 15 vertically, in agreement with the calculations. The measured photon-flux density is 104 photons/(s mA μm2), suited for detecting trace elements of sub-ppm concentration in an organic matrix with a detection volume of the order of 10 μm diameter.

Switchable lenticular based 2D/3D displays

The use of an LCD equipped with lenticular lenses is an attractive route to achieve an autostereoscopic multi-view 3D display without losing brightness. However, such a display suffers from a low spatial resolution since the pixels are divided over various views. To overcome this problem we developed switchable displays, using LC-filled switchable lenticulars. In this way it is possible to have a high-brightness 3D display capable to regain the full native 2D resolution of the underlying LCD. We showed the feasibility of LC-filled switchable lenticulars in several applications. For applications in which it is advantageous to be able to display 3D and 2D on the same screen, we made a prototype having a matrix electrode structure. A problem with LC-filled lenses is that in the 2D state there is a residual lens effect at oblique angles. This effect and a possible solution are discussed as well.

Applications of Glancing Incidence X-Ray Analysis

In many technological applications layered materials have an increasing importance. Almost complete characterization of such materials can be achieved with glancing incidence x-ray analysis (GIXA). Within this technique, x-ray reflectivity and angle-dependent x-ray fluorescence measurements are combined, resulting in a structural and chemical analysis of the samples.