Nadja Felde

Light scattering in poly (vinyl alcohol) hydrogels reinforced with nanocellulose for ophthalmic use

Scattering of ophthalmic devices is a complex phenomenon involving both surface and bulk light-material interactions. In this work, light scattering of nanocellulose reinforced PVA hydrogels contac ...

Scattering properties of hot isostatic pressed multispectral zinc sulfide

A common window material for applications that require the simultaneous use of visible and infrared wavelengths is zinc sulfide, which offers a high transmittance between 400 nm and 12 μm. Depending on the manufacturing process, zinc sulfide can, however, exhibit large scattering losses (>10%) which degrade the imaging quality in particular in the visible spectral range. In this contribution, the different sources for light scattering such as volume imperfections, surface roughness, and subsurface damage are analyzed individually for hot isostatic pressed chemical vapor deposited zinc sulfide and correlated to the structural properties resulting from the fabrication process.

Defined wetting properties of optical surfaces

Abstract Optical surfaces equipped with specific functional properties have attracted increasing importance over the last decades. In the light of cost reduction, hydrophobic self-cleaning behavior is aspired. On the other side, hydrophilic properties are interesting due to their anti-fog effect. It has become well known that such wetting states are significantly affected by the surface morphology. For optical surfaces, however, this fact poses a problem, as surface roughness can induce light scattering. The generation of optical surfaces with specific wetting properties, hence, requires a profound understanding of the relation between the wetting and the structural surface properties. Thus, our work concentrates on a reliable acquisition of roughness data over a wide spatial frequency range as well as on the comprehensive description of the wetting states, which is needed for the establishment of such correlations. We will present our advanced wetting analysis for nanorough optical surfaces, extended by a vibration-based procedure, which is mainly for understanding and tailoring the wetting behavior of various solid-liquid systems in research and industry. Utilizing the relationships between surface roughness and wetting, it will be demonstrated how different wetting states for hydrophobicity and hydrophilicity can be realized on optical surfaces with minimized scatter losses.

Mechanically Durable Optical Coatings with Adjustable Wetting Properties

Realization of durable functional surfaces with high optical quality requires a careful control of the relevant roughness components. An efficient fabrication procedure for generating such nanorough coatings and their properties will be presented.