02-04-2013, SCHOTT North America
SCHOTT Identifies Alternative Glass Materials for High-Power Laser Applications
SCHOTT characterizes the bulk laser damage threshold of its optical glasses for use in industrial high-power applications
ELMSFORD, N.Y. and SAN FRANCISCO – February 5, 2013 –The SCHOTT technology group will present new data on the bulk laser damage threshold (LDT) of various glasses, including viable alternatives to fused silica for high-power applications, at SPIE Photonics West. The glasses tested are intended for use in material processing at wavelengths of 532 and 1064 nm with pulse lengths in the nano- and picosecond range. As a leading specialized glass manufacturer, SCHOTT has been enabling advancements in the optical industry for more than 125 years.
“The lasting efficiency of a laser system depends on the surface quality of its optical components, but just as important is the lens material, which needs to withstand laser beams and reflections,” said Dr. Ralf Jedamzik, Application Manager at SCHOTT. “Fused silica is the current material of choice for high-power applications. However, it limits optical designs due to its low refractive index and high price. Our new data on the bulk laser damage threshold of optical glasses suggests interesting alternatives.”
One of the driving forces in the global laser market is the development of next-generation laser technology that can provide a high-energy beam even at a very high repetition rate in a very short period of time. In order to facilitate and optimize the optical design of these new systems, SCHOTT has now examined the bulk laser resistance of its most suitable glasses for high-power applications.
Optimizing lens designs
SCHOTT tested various glass types covering a broad range of refractive indices and Abbe numbers to obtain information on their bulk property differences. The tests, which were carried out at the Laser Zentrum Hannover e.V., one of Europe’s leading research and development institutes in the field of laser technology, used Heraeus Holdings’ fused silica Suprasil CG. SCHOTT worked with Qioptiq, a designer and manufacturer of photonic products and solutions, to optimize its LINOS F-Theta-Ronar lenses with respect to performance and cost.
“We learned that glasses with lower Abbe numbers tend to have lower laser damage thresholds—though there are exceptions, like F2. And in comparison to flint glasses like SF6, high refractive index glasses like N-LASF44 and N-LAF21 show a higher laser resistance,” Dr. Jedamzik said. “But most importantly, the glass types N-BK7 and N-FK5 showed very good behavior compared to Suprasil. With respect to the test conditions, these glass types can be considered as alternatives to fused silica.”
Expanding the scope
The glass types N-BK7, N-FK5, F2, N-LAF21, N-LASF44, and SF6 were tested at wavelengths of 532 nm and 1064 nm, and at pulse widths of 10 to 12 ns and 74 ps—common in pulsed laser material processing. According to DIN ISO 21254, 150 test sites were investigated.The incoming beam diameters of 5-6 and 10 mm were each separately focused in the center of the sample to an effective spot diameter of 33 to 41 μm depending on the wavelength, to exclude surface influences.
“The published results already enable an optimized design of the F-Theta lens if the actual laser loads are known in the optical path,” Dr. Jedamzik said. “Our customers can now directly access the available data, facilitating the selection of appropriate materials for their applications. In the near future, SCHOTT plans to extend its investigations to other glass types and components with respect to upcoming industrial and scientific laser projects.”
Suprasil CG is a registered trademark of Heraeus Holdings, GmbH
Visit SCHOTT at SPIE Photonics West at booth #1600, and attend the following lectures and product demonstrations:
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