Tobias Kresse

Computer-generated stratified diffractive optical elements

We present what is to our knowledge a new type of diffractive optical element (DOE), the computer-generated stratified diffractive optical element (SDOE), a hybridization of thin computer-generated DOEs and volume holograms. A model and several algorithms for calculating computer-generated SDOEs are given. Simulations and experimental results are presented that exhibit the properties of computer-generated SDOEs: the strong angular and wavelength selectivity of SDOEs makes it possible to store multiple pages in a computer-generated SDOE, which can be read out separately (multiplexing). The reconstruction of an optimized SDOE has a higher quality than the reconstruction of optimized one-layer DOEs. SDOEs can be calculated to have only one diffraction order.

Laser writing on oriented polymer films

Polymer films are suitable substrates for optical data storage due to their mechanical and optical properties. Furthermore, oriented polymer films show an additional effect to laser writing. In this review the effects of laser writing on oriented polymer films are investigated by atomic force microscopy. A change in surface topography of the film is observed. Different polymer types and different draw ratios are used. The dependence of topography effects on the draw ratio is shown. A model of the writing effect is framed.

tesa ROM and tesa WORM: multilayered optical data storage based on polymer films and using metal island films as tunable absorber system

A new optical data storage medium is introduced. Its cylindrical shape and multi-layer storage allows a storage capacity of ~ 3.5 GByte at a radius and a height of 15 mm. Metal island films are used as a tunable absorber system for multi-layer storage. The proposed absorber system provides high reflection and high absorption for each layer during the writing process. For the reading process the optical properties of each layer can be tuned to appropriate values. Results of a five-layered ROM as well as concept and first results of a five-layered WORM are given.

Local adjustment of the optical properties of metal island films by means of a laser

Metal island films are widely-used as reflection layers in optics and optical data storage. Their optical properties are dominated by the effect of plasmon resonance and, thus, by size and shape of the metal islands. By altering size and shape of these islands, the optical properties of the metal films can be adjusted. Depending on the wavelength range and type of metal, the film reflectance can be either increased or decreased. It is shown that changes in size and shape can be caused by means of a laser. This allows a well-defined adjustment of the optical properties of thin metal films. The optical properties can be adjusted locally. This technique can be used in different fields such as holography, adaptive optics or multi-layer optical data storage.