Search

We introduce the concept of chromatism compensation in nulling interferometry that enables a high rejection ratio in a wide spectral band. Therefore the achromaticity condition considered in most nulling interferometers can be relaxed. We show that this chromatism compensation cannot be applied to a two-beam nulling interferometer, and we make an analysis of the particular case of a three-telescope OCIS codes: 120.3180, 350.1260.

Extreme ultraviolet (EUV) lithography uses reflective ring-field projection systems. Geometrical obstruction limits the possible system configurations to small domains of the parameter space. We present an analysis, a search method, and a classification of these unobstructed domains. The exhaustive search method based on paraxial analysis provides an effective means for determining all possible design forms and for finding useful starting configurations for optimization. The approach is validated through comparison with finite ray tracing. OCIS codes: 080.2740, 110.3960, 340.7440.

In this theoretical study we show that by removing or depositing additional multilayer (ML) periods of a thin-film interference coating, distortions in the reflected wave front induced by surface figure errors can be corrected. At [lambda] = 13.4 nm in the extreme-ultraviolet region the removal or deposition of a single period of the standard two-component molybdenum-silicon (Mo/Si) ML interference coating induces an effective phase change of magnitude 0.043 [pi] with respect to an identical optical thickness in vacuum. The magnitude of this wave-front shift can be enhanced with multicomponent MLs optimized for phase change on reflection. We briefly discuss the contributions of the shift in the effective reflection surface of the ML on the phase change. We also predict the feasibility of novel phase-shifting masks for subwavelength imaging applications. OCIS codes: 160.3900, 230.4170, 310.6860, 340.7470.

Direct detection of exoplanets is possible by use of a technique called nulling interferometry, which is based on destructive interference of light of the bright object and constructive interference of the faint object. In the infrared wavelength region, this implies that light of a star must be attenuated by a certain factor, the so-called rejection ratio, which typically equals [10.sup.6]. This can be achieved by use of phase shifters, which apply a phase shift of [pi] rad with an average error no greater than 2 mrad over a predefined wavelength region. For a 6-18-[micro]m wavelength interval, this is a tough constraint. We show that the 2-mrad constraint can be relaxed if more than two beams participate in the beam recombination. We focus our attention on dispersive phase shifters and show that rejection ratios beyond [10.sup.6] can be reached easily by use of a system of four or more apertures and simple dispersive phase shifters that consist of only one material. OCIS codes: 350.1260, 120.3180.

In a new type of illumination system for reflective liquid-crystal displays, the frontlight, unwanted shadows appear in certain viewing directions. It will be shown that for an accurate description of these shadows the geometrical optics approach is not satisfactory and that Fresnel diffraction has to be taken into account. A model for the diffraction effects was developed, and the predicted results correspond well to the measurements. In addition, some remarkable effects were explained from the theory of Fresnel zones. OCIS codes: 050.1940, 350.3950, 230.3990.

In the infrared wavelength region, a typical star is approximately a million times brighter than the planet that surrounds it, which is a major problem when we attempt to detect exoplanets in a direct manner. Nulling interferometry is a technique that one can use to solve this problem by attenuating the stellar light and enhancing that of the planet. Generally, deep nulling is achieved by use of achromatic phase shifters (APSs). Unfortunately, the technology needed to build these APSs is not yet fully developed. We show that deep nulling can also be achieved by using delay lines only. We investigate the nulling depth as a function of the width of the wavelength interval and the number of telescopes. We also show that we can obtain nulling depths of less than [10.sup.-6], which are required for exoplanet detection. Furthermore, we investigate the properties of the transmission map and make a comparison between our system and an APS system.

We report on a way to shape surfaces with fluid jet polishing by adjusting the influence function (the shape of the footprint of the nozzle) instead of changing the dwell time of the nozzle on the surface. In that way, the surface is processed homogeneously, and no dip is generated in the center of the workpiece. As a proof of this approach, a [lambda]/10 flat surface has been generated in our laboratory. OCIS codes: 220.4610, 240.6700.

We report on what we believe to be a novel classification method for polishing processes that we apply in our laboratory on a regular basis. Two parameters are deduced from the in situ iTIRM (intensity-detecting total-internal-reflection microscopy) measurement method. Contrary to Preston's law, which gives the removal rate, the parameters of the iTIRM process are a measure of the change in surface quality (roughness, subsurface damage, and scratch and dig) and the duration of the polishing process. OCIS codes: 120.4800, 120.4630, 220.5450, 120.4610, 120.4290.