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Proceedings Paper

Optical autofocus for high resolution laser photoplotting
Author(s): Jose Alonso; Daniel Crespo; Isidoro Jimenez; Eusebio Bernabeu
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Paper Abstract

An all optical autofocus has been designed and tested for tight line width control in a high NA laser photoplotter system. The laser system is based in a GaN semiconductor laser with power 30 mW and wavelength 405 nm. The advantage of using this laser, despite the relatively long wavenlength, is compactness and easy for high frequency modulation. The autofocus system is based in a secondary 635 nm GaAlAs laser without need for wavelength, neither power stabilization. The two beams are delivered coaxially through the focusing lens by means of a dichroic beamsplitter. Focusing lens need no correction for chromatic aberration, as this is compensed by appropriate autofocus beam divergence. After reflection in the sample, the autofocus beam is separated from the returning writing beam and then guided to a collimation sensor, in which defocus of about 1/20 of the Rayleigh range of the writing beam can be detected and compensated by an analogue PID electronic control. Stable linewidth within 5% is achieved with different numerical aperture focusing lenses.

Paper Details

Date Published: 7 July 2005
PDF: 8 pages
Proc. SPIE 5840, Photonic Materials, Devices, and Applications, (7 July 2005); doi: 10.1117/12.628138
Show Author Affiliations
Jose Alonso, Univ. Complutense de Madrid (Spain)
Daniel Crespo, Indizen Technologies S.L. (Spain)
Isidoro Jimenez, Univ. Complutense de Madrid (Spain)
Eusebio Bernabeu, Univ. Complutense de Madrid (Spain)

Published in SPIE Proceedings Vol. 5840:
Photonic Materials, Devices, and Applications
Goncal Badenes; Derek Abbott; Ali Serpenguzel, Editor(s)

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