25 April 2006 Grayscale fabrication errors and their impact on beam shaper performance
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Abstract
Employing a grayscale technology for the realization of complex diffractive optical structures does not guarantee superior performance. Even slight variations in etch depth, structure radient or surface geometry can be disastrous to the performance of the element once fabricated. Grayscale structures, such as blazed structures are specifically complicated because the fabrication process must take into account and maintain consistency of materials, photo resist, lithography, and etch process from batch to batch. Engineers who look to implement grayscale diffractive technology need to be conscious of these latent errors and how they emerge during the fabrication process. This paper will present a case study on a beam shaper design which was fabricated in three different batches per year (2001, 2004 and 2005) over a 5 year period. Each batch utilized a grayscale mask (manufactured in 2000, used in 2001) and its established process recipe to fabricate the optical elements from each of these batches. Specific data will be presented covering optical design and modeling data and its comparison to data of actual testing of the elements. An overview will be presented covering the optical testing and metrology techniques used to verify the optical performance and dimensional stability of grayscale structures forming the optical element. In conclusion, a synopsis of potential solutions for verification of process stability and repeatability prior to committing to final fabrication will be offered to engineers seeking to use grayscale technology.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Todd E. Lizotte, Todd E. Lizotte, } "Grayscale fabrication errors and their impact on beam shaper performance", Proc. SPIE 6187, Photon Management II, 61870N (25 April 2006); doi: 10.1117/12.661396; https://doi.org/10.1117/12.661396
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