17 September 1999 Formation of diffractive optics in photopolymer films by direct laser beam writing
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Abstract
Dry photopolymerizable thin films are used to fabricate diffractive optical elements for application in the infrared wavelength region. The polymer solution consists of polyvinyl alcohol (PVA) as a binder, acrylamide (AA) as the monomer base, triethanolamine as a coiniciator, and methylene blue as a photo sensitizer. Such PVA/AA thin films are prepared on glass substrates by graving settling and drying in the dark for about 15 hours, leading to film thicknesses of about 50 microns. The drying of the films is controlled by permanent weighting of the samples. In this way a defined water content can be adjusted, and the sample properties are well reproducible. The photopolymer films are exposed with a laser beam writing system, consisting of a focused helium neon laser beam and computer controlled linear stages that move the photopolymer film in its plane with a resolution of one micron. Computer-generated diffraction patterns are reproduced directly into the photosensitive films. Regulation of the laser illumination is achieved by controlling the speed of the linear stages. The formation of the relief structure with amplitudes up to 10 microns, i.e., 20 percent of the film thickness, takes place in the dark by self-development without the need of wet chemical processing. As a last processing step, the samples are illuminated homogeneously to passivate the photo sensitizer and to fix the obtained relief structure.
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Detlef Kip, Jens Neumann, "Formation of diffractive optics in photopolymer films by direct laser beam writing", Proc. SPIE 3778, Gradient Index, Miniature, and Diffractive Optical Systems, (17 September 1999); doi: 10.1117/12.363754; https://doi.org/10.1117/12.363754
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KEYWORDS
Polymers

Diffractive optical elements

Helium neon lasers

Infrared radiation

Polymer thin films

Thin films

Carbon dioxide lasers

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