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Formation of micro-optical structures by self-writing processes in photosensitive polymers

: Streppel, U.; Dannberg, P.; Wächter, C.; Bräuer, A.; Kowarschik, R.


Applied optics 42 (2003), No.18, pp.3570-3579
ISSN: 0003-6935
ISSN: 1539-4522
ISSN: 1559-128X
Journal Article
Fraunhofer IOF ()
self-writing; self-organization; optical polymer; UV sensitivity; pattern formation; filamentation

A local exposure of UV-sensitive polymers leads to a local curing. This correspo nds to a saturable and irreversible nonlinear change of the refractive index, wh ich evidently leads to a filamentation of the hardening polymer. This paper inve stigates the physical background of these effects and analyzes how the different influencing factors could be used for a steered, partly self-written formation of microoptical structures. The structure formation is simulated on the basis of an iterative beam propagation method with consideration of a set of process par ameters, e.g., the photoinitiator concentration or the exposure intensity. It is shown theoretically as well as experimentally that a variation of material- and exposure-specific process parameters gives opportunities for a controlled struc ture formation. The experimental realization of a configuration by use of a beam shaper within a LTV contact exposure process is presented by means of the prepa ration of high-aspect-ratio conic structures.