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

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.”

Visit SCHOTT at SPIE Photonics West at booth #1600, and attend the following lectures and product demonstrations:

• Optical Materials for Microscopy Design 
  Glass with large anomalous partial dispersion and low dispersion for best color correction-high transmittance glass improves light transmittance at the UV-edge—pure raw materials for low fluorescence. 
  Sunday, 3 February 2013, 11:30 a.m. 
  BiOS, Demo Area 
  Dr. Ralf Jedamzik, SCHOTT Advanced Optics
• Recent Results on Bulk Laser Damage Threshold of Optical Glasses 
  Project for characterization of bulk LDT of optical glasses at wavelengths 532 nm and 1064 nm with pulse lengths in the nano- and pico-second range. Description of measurement approach and presentation of results. 
  Tuesday, 5 February 2013, 4:20 p.m. 
  LASE, Room: 124, Exhibit Level 
  Dr. Ralf Jedamzik, Frank Elsmann, SCHOTT Advanced Optics
• “Zerodur” goes Extreme 
  Zerodur Extreme glass-ceramic offers the tightest CTE tolerance on the market. Zerodur Tailored glass-ceramic is optimized to final application temperature profiles and presented as 1.2 m ultra-light weighted Zerodur glass-ceramic piece. 
  Wednesday, 6 February 2013, 3:30 p.m. 
  Photonics West, Demo Area 1 @ South Hall ABC 
  Dr. Ralf Jedamzik, SCHOTT Advanced Optics
• Perfect Filters and Designs for Demanding Customized Applications 
  Portfolio extension including new filter glass sets, interference filters and new designs and introduction of new filter calculation program and catalog. 
  Thursday, 7 February 2013, 11:30 a.m. 
  Photonics West, Demo Area 1 @ South Hall ABC 
  Dr. Ralf Biertuempfel, SCHOTT North America Inc.
• Laser Damage Threshold of Optical components 
  Laser damage threshold of components depends on surface quality and material properties – we now define this threshold of optical glass and present data on high reflective broadband coatings and components. 
  Thursday, 7 February 2013, 2:30 p.m. 
  Photonics West, Demo Area 1 @ South Hall ABC 
  Dr. Todd Jaeger, SCHOTT North America Inc.

Download link to a ZIP file that contains this photograph in print quality: http://www.schott-pictures.net/presskit/189519.laserdamagethreshold

About SCHOTT
SCHOTT is an international technology group with more than 125 years of experience in the areas of specialty glasses and materials and advanced technologies. SCHOTT ranks number one in the world with many of its products. Its core markets are the household appliance, pharmaceuticals, electronics, optics, solar power, transportation and architecture industries. The company is strongly committed to contributing to its customers’ success and making SCHOTT an important part of people’s lives with high-quality products and intelligent solutions. SCHOTT is committed to managing its business in a sustainable manner and supporting its employees, society and the environment. The SCHOTT Group maintains close proximity to its customers with manufacturing and sales units in all major markets. Its workforce of around 17,000 employees generated worldwide sales of $4B (approximately 2.9 billion euros) for the 2010/2011 fiscal year.