Michael Helgert

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We report an innovative approach for the fabrication of highly light transmissive, antireflective optical interfaces. This is possible due to the discovery that metallic nanoparticles may be used as a lithographic mask to etch nonstraightforward structures into fused silica, which results in a quasihexagonal pattern of hollow, pillar-like protuberances. The(More)
In this paper, we present a broadband wire grid polarizer with a spectral working range down to a wavelength of 193 nm. Tungsten is chosen as grating material because it provides a high extinction ratio and transmission compared with other common grating materials. The fabrication of the grating with 100 nm period was accomplished using a spatial frequency(More)
Antireflective surfaces composed of biomimetic sub-wavelength structures that employ the 'moth eye principle' for reflectance reduction are highly desirable in many optical applications such as solar cells, photodetectors and laser optics. We report an efficient approach for the fabrication of antireflective surfaces based on a two-step process consisting(More)
Al(2)O(3) and TiO(2) thin films have been deposited on Si wafers, quartz, BK7 glass, and polycarbonate substrates by atomic layer deposition (ALD). The refractive indices and growth rates of the materials have been determined by spectroscopic ellipsometry and transmission electron microscopy. The influence of substrate temperature and precursor on the(More)
Laterally structured antireflective sub-wavelength structures show unique properties with respect to broadband performance, damage threshold and thermal stability. Thus they are superior to classical layer based antireflective coatings for a number of applications. Dependent on the selected fabrication technology the local topography of the periodic(More)
A flexible, nondestructive, and cost-effective replication technique for nanostructures is presented. The advantages of the process are: 1) it allows for tailoring structural parameters of the replica (e.g., line width) nearly independent of the structural geometry of the master; 2) it allows for replication of high-aspect-ratio structures also in polymer(More)
We present transmission increased fused silica lenses produced by using self-organized antireflective structures for which we developed an efficient manufacturing process. The spectral transmission measured over the whole lens aperture shows a significant transmission enhancement of up to 3.5% in the UV range. Local measurements on the lens's surface reveal(More)
Antireflective subwavelength structures (ARS) resembling nanostructures found on the cornea of night-active insects reduce the reflection of light by providing a gradual change in the refractive index at the interface. These artificial ARS have mainly been fabricated by a combination of conventional lithography and reactive ion etching, which constrains(More)
We fabricated stochastic antireflective structures (ARS) and analyzed their stability against high power laser irradiation and high temperature annealing. For 8 ps pulse duration and 1030 nm wavelength we experimentally determined their laser induced damage threshold to 4.9 (±0.3) J/cm(2), which is nearly as high as bulk fused silica with 5.6 (±0.3)(More)
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