Hugo Johan Cornelissen

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.

Electron beam pumped lasing in ZnSe/ZnSSe superlattice structuresn grown by molecular‐beam epitaxy

We report the first operation of molecular‐beam epitaxy (MBE) grown ZnSe/ZnSxSe1−x superlattice electron beam pumped lasers in the temperature range 100–300 K and the first room‐temperature operation of MBE grown ZnSe on GaAs transverse geometry electron beam pumped lasers. Threshold current densities of 2.5 A/cm2 at 100 K were achieved by both devices. At room temperature, threshold current was 5 A/cm2 for the ZnSe devices and 12 A/cm2 for the superlattice.

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.

Towards a polarized light-emitting backlight: micro-structured anisotropic layers

— A backlight for liquid-crystal-display illumination is presented, in which s-polarized light is preferentially coupled out by micro-optical structures in a birefringent layer. In the experiments, contrasts higher than 15 have been obtained. A polarization dependent ray-tracing model has been developed. Important guidelines for finding an optimal backlight configuration have been derived from the calculations.

Linearly polarized light-emitting backlight

A new polarized backlight system for liquid-crystal displays (LCDs) is presented in which one linear polarization is preferentially coupled out by anisotropic scattering. The lightguide consists of a polymeric polarization-dependent scattering film adhered to a transparent polymeric substrate. By changing the scattering power of the film, the polarized light outcoupling angles can be influenced and optimized to achieve a maximum outcoupling centered along the normal direction. The other linear polarization is mainly trapped in the lightguide and is shown to be recycled to enhance the overall light and/or energy efficiency. With a proper substrate choice, the achieved local contrast exceeds 14 over a 50-mm range. A collimated light input further enhances the polarized contrast to well over 17.

45.3: Micro-structured Polymeric Linearly Polarized Light Emitting Lightguide for LCD Illumination

A new linearly polarized light emitting lightguide system is presented, consisting of a micro-structured anisotropic polymer film which is coated with an isotropic layer and adhered to a transparent polymeric substrate. With conventional edge-lighting of the lightguide very high polarized contrasts are realized, exceeding 100. A gain in efficiency can be achieved by recycling of the trapped light with the orthogonal polarization.

38.3: Polarized Light LCD Backlight Based on Liquid Crystalline Polymer Film: A New Manufacturing Process

A backlight for liquid crystal display illumination is presented, consisting of a commercial birefringent liquid crystalline polymeric layer innovatively laminated onto a micro-structured plastic light guide. S-polarized light is preferentially extracted from the light guide, and the efficiency was measured to be 1.78 time higher than in for a conventional unpolarized light emitting backlight.

Quantum confinement and strain effects in ZnSe‐ZnSxSe1−x strained‐layer superlattices

A photoluminescence study of ZnSe‐ZnSxSe1−x strained‐layer superlattices with x=0.19 grown by molecular beam epitaxy is presented. We observe clear shifts of the excitons to higher energies as the well widths are reduced. These shifts are interpreted in terms of quantum confinement effects using the envelope function approach and the strain‐induced effects using the deformation potential theory. From our analysis we conclude that most of the band offsets between ZnSe‐ZnSxSe1−x are taken up by the valence bands.

Phosphor-converted LED modeling using near-field chromatic luminance data

A new method of creating a source model of a phosphor-converted white LED is demonstrated. It is based on a simple phosphor model, of which some key parameters have been obtained from measuring the near-field chromatic and luminance characteristics of a complete LED. The accuracy of the model is verified by measurements and simulations on an LED with a ball lens as primary optic.

Electron density in low-pressure Na-Ne discharges deduced from laser absorption experiments

Laser absorption experiments are described to measure the radial sodium ground‐state distribution in the positive column of a low‐pressure Na‐Ne discharge. The radial electron density distribution is obtained by combining the results with a particle balance. The electron densities at the tube axis n e (0) derived in this way are approximately a factor of 2.5 higher than the ones derived from a direct determination with Langmuir probes.Measuring the sodium profiles as a function of the distance to a probe reveals quantitatively the perturbative effect on the plasma of the glass capillary that supports the probe. This partly explains the observed discrepancy in n e (0). The electron temperatureT e is deduced from the laser absorption data using the measuredelectrical conductivity of the plasma. This value of T e agrees very well with the value as measured with the probe.