Iridescent colors created by sophisticated nanostructured materials are known from nature and attract a lot of attention
nowadays. A closer look reveals that such colors are often produced by combination of structures at different lengths
scales at the micrometer and nanometer level. While simulation and analysis of such structures can be done with
rigorous methods fabrication is seldom attacked because if its complexity. We have chosen a particular design concept
that uses Bragg reflectors as dispersive components and microoptical elements to steer the light. We focused on
fabrication in organic materials, where compatibility of different process steps is an issue. Fabrication is done by spin-coating
of thin films and soft replication of microoptical elements. The structures were entirely fabricated in polymer
materials on glass substrates or polymer films that serve as substrates. Microoptical structures with dimensions ranging
from 30 to 250 microns are embossed on Bragg reflectors having periods of 160 nm. Of main interest for us were the
spectral reflection properties. Reflection properties were measured for white light in a goniometric setup and their
behavior is discussed. To understand the basic features modeling is carried out by combining ray tracing and rigorous
With help of liquid crystal polymers (LCP) a polarization sensitive diffuser has been realized. By using convex
microstructures made of LCP and an index matching layer, two distinct functions depending on the orientation of the
device and the polarization state of the input light are realized. For one polarization the light pass through the device
with no changes and for the perpendicular polarization, the light is diffused by the microstructures.
Refractive, diffractive and reflective micro-optical elements for laser beam shaping and homogenizing have been manufactured and tested. The presented multifunctional optical elements are used for shaping arbitrary laser beam profiles into a variety of geometries like, a homogeneous spot array or line pattern, a laser light sheet or flat-top intensity profiles. The resulting profiles are strongly influenced by the beam properties of the laser and by diffraction and interference effects at the micro-optical elements. We present general design rules for beam shaping and homogenizing. We demonstrate the application of such multifunctional micro-optical elements for a variety of applications from micro-laser machining to laser diagnostic systems.
The optical properties of plano-convex refractive microlenses with low Fresnel Number (Typically FN < 10) are investigated. Diffraction effects at the lens stop limit the range of the effective focal length. The upper limit of the focal length is determined by the diffraction pattern of a pinhole with equal diameter. Refraction and diffraction have antagonist effects on the focal length when changing the wavelength of illumination. Diffraction effects at the lens stop are used to balance dispersion and to design microlens achromats. Gaussian beam propagation method has been used for simulation. The presented results are of relevance for applications like Shack Hartmann wavefront sensors or confocal microscopes, where microlenses with small apertures and long focal lengths are widely used.