The spectrally selective optical properties of wavelength selective radiation emitters and ® lters based on periodically microstructured metal surfaces were investigated. Metal surfaces were structured by the use of a holographic mask and subsequent etching processes. Due to the microstructure, thermally excited surface plasmons couple to electromagnetic radiation. Therefore a structured tungsten surface can act as a selective radiation emitter. The calculation of the absorptance by a rigorous diå raction theory allows the prediction of the emissivity of such structures. The angle dependent emissivity of tungsten gratings with periods of 1.4 m m and 2.0 m m was measured. A peak emissivity of 70%at a wavelength of 1.6 m m was achieved. Band pass ® lters for the near infrared spectral range based on perforated metal ® lms were investigated theoretically and experimentally. Filters with a grating period of 2.0 m m were produced. A peak transmittance of 80% at a wavelength 2.9 m m was achieved. The optical properties of the diå ractive elements described partly show a strong angle dependence IntroductionIn this contribution we investigate the optical properties of periodically microstructured metallic surfaces. The goal is to manufacture radiation ® lters and emitters for the near infrared (NIR) spectral range, that show wavelengthselective optical properties based on resonance eå ects.Our work was initially motivated by the use of selective emitters and bandpass ® lters in thermophotovoltaic (TPV) systems [1]. In a TPV generator, a thermal emitter is driven by any heat source with a suae cient temperature. The radiation of the emitter is converted into electrical energy by a photovoltaic (PV) cell. One of the major challenges of current research work on TPV systems is to reduce the mismatch between the emission spectrum and the spectral sensitivity of the PV cell. This can be done by increasing the emissivity of the emitter at convertible photon energies and by ® ltering the radiation.The selective emitters which we investigated are based on the eå ect that on structured surfaces thermally excited surface plasmons can be converted to electromagnetic radiation. This leads to an increase of the emittance of a metallic surface in a limited spectral range. The kind of surface structure determines the spectral range of the emissivity maxima. Towards longer wavelengths the grating

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Antiglare AG and low‐ or anti‐reflection LR, AR are important optical features of the front surfaces of flat panel displays and other information displays. New types of holographic surface relief microstructures have been developed on large areas showing very good optical properties. Holographic exposure techniques give the freedom to carefully design AG properties. They also allow the superposition of different types of structures, e.g. a Motheye AR and an AG microstructure MARAG ™ 1, which can be produced very cost‐effectively by mass UV precision nano‐replication UV‐PNR. As a bonus, the UV‐PNR structures are hardcoat materials suitable for the real world.

The availability of periodic surface-relief structures with grating constants from 200 nm to 100 microns on large areas leads to a wide field of applications. Effects of interest are the antireflection properties of high aspect ratio subwavelength gratings and the light management by structures in the micrometer scale. The size of the homogeneously structured area and the ease of producability is decisive for the commercialisation of such functional surfaces. Microstructures like these can be produced on large areas by holographic exposure processes. Subsequent holographic exposures with differing parameters lead to combined structures with distinct properties. Master structures in photoresist can be used to fabricate nickel stampers. Techniques like UV roller casting and hot embossing can be employed to replicate such microstructures on large areas with high precision. With such replication processes a very cost effective mass production is possible. With our holograph ic set-up periodic surface relief structures with various grating types and profile shapes can be realised with a good homogeneity on an area with dimensions up to 600 × 800 mm2. The combination of stochastic and periodic structures offers the chance to obtain a multifunctional surface with antiglare and broadband antireflection properties. The possible applications are solar energy systems, lighting or displays

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Microstructured films as optical components have become more and more important for information displays recently. Such films can act as light management components, that distribute light uniformly in LC displays or on rear projection screens. Glare control and AR can be achieved using microstructures on the front surface of displays. Recently developed large area holographic exposure techniques combined with mass replication allow a very precise definition of the optical properties of such light-weight, cost-effective films..

The design of the front surface of a display, the interface to the viewer, requires careful selection of materials and coatings. The most prominent requirements for the front surface material are reflection or glare treatment, scratch resistance and of course a good optical appearance. Different types of optical films and coatings are available with different types of antireflection systems. This article gives an overview over available antireflection (AR) systems and compares their performance and their limitations. The comparison covers interference AR coatings made by thin film deposition either by evaporation or from liquid phase (sol‐gel), single and multilayer thin film systems, graded index profile systems (porous and motheye), antiglare (AG) and combined AG/AR systems.