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Proceedings Paper

Multilevel diffractive optical element manufacture by excimer laser ablation and halftone masks
Author(s): Francois Quentel; Jim Fieret; Andrew S. Holmes; Sylvain Paineau
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Paper Abstract

A novel method is presented to manufacture multilevel diffractive optical elements (DOEs) in polymer by single- step KrF excimer laser ablation using a halftone mask. The DOEs have a typical pixel dimension of 5 micrometers and are up to 512 by 512 pixels in size. The DOEs presented are Fresnel lenses and Fourier computer generated holograms, calculated by means of a conventional iterative Fourier transform algorithm. The halftone mask is built up as an array of 5 micrometers -square pixels, each containing a rectangular or L- shaped window on an opaque background. The mask is imaged onto the polymer with a 5x, 0.13 NA reduction lens. The pixels are not resolved by the lens, so they behave simply as attenuators, allowing spatial variation of the ablation rate via the window size. The advantages of halftone mask technology over other methods, such as pixel-by-pixel ablation and multi-mask overlay, are that it is very fast regardless of DOE size, and that no high-precision motion stages and alignment are required. The challenges are that the halftone mask is specific to the etch curve of the polymer used, that precise calibration of each grey-level is required, and that the halftone mask must be calculated specifically for the imaging lens used. This paper describes the design procedures for multilevel DOEs and halftone masks, the calibration of the various levels, and some preliminary DOE test results.

Paper Details

Date Published: 29 June 2001
PDF: 12 pages
Proc. SPIE 4274, Laser Applications in Microelectronic and Optoelectronic Manufacturing VI, (29 June 2001); doi: 10.1117/12.432538
Show Author Affiliations
Francois Quentel, Thomson-CSF (France)
Jim Fieret, Exitech Ltd. (United Kingdom)
Andrew S. Holmes, Imperial College of Science, Technology and Medicine (United Kingdom)
Sylvain Paineau, Thomson-CSF (France)


Published in SPIE Proceedings Vol. 4274:
Laser Applications in Microelectronic and Optoelectronic Manufacturing VI
Malcolm C. Gower; Henry Helvajian; Koji Sugioka; Jan J. Dubowski, Editor(s)

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