Design and realization of advanced multi-index systems.

Practically all thin film systems for normal incidence can be realized using only two-layer materials. But for oblique incidence, polarization effects occur, designs may become complex, and polarization control is difficult or impossible to achieve. Here multi-index or gradient designs offer additional degrees of freedom, and can simplify or even enable challenging designs.

Antireflective subwavelength structures on microlens arrays-comparison of various manufacturing techniques.

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 their application to planar substrates. We report on the fabrication of ARS using three different techniques including bottom-up and top-down methods as well as their combination on microlens arrays (MLAs) made of fused silica.

Simulating different manufactured antireflective sub-wavelength structures considering the influence of local topographic variations.

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 structure may deviate from the perfect repetition of a sub-wavelength unit cell.

Tailored antireflective biomimetic nanostructures for UV applications.

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 of gold nanoparticle mask generation by micellar block copolymer nanolithography and a multi-step reactive ion etching process. Depending on the RIE process parameters nanostructured surfaces with tailored antireflective properties can easily be fabricated that show optimum performance for specific applications.

Biomimetic interfaces for high-performance optics in the deep-UV light range.

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 far reaching optical performance of these structures is demonstrated by reflection and transmission measurements at oblique angles of incidence over a broad spectral region ranging from deep-ultraviolet to infrared light.

Synthesis, complexation, and coordination oligomerization of 1,8-pyrazine-capped 5,12-dioxocyclams.

(Methyl)(methoxy)-5,12-dioxocyclam 1 was alkylated on the secondary amines (capped) with 2,6-bis(bromomethyl)pyrazine. The resulting macrocycle was complexed to copper(II) to produce a five-coordinate complex 5a which was fully characterized by a range of spectroscopic methods (IR, UV-vis, ESR) as well as by X-ray crystallography. The structure of this complex is similar to the previously reported pyridine complex, with the five-coordinate copper having distorted square pyramidal geometry and a Cu-Pz bond length of 2.