Pulse-length dependence of absorptance and degradation rate of fused silica at 248 nm
- Laser-Laboratorium Goettingen e.V. (Germany)
- Heraeus Quarzglas GmbH, Hanau (Germany)
Optical components for industrial excimer laser applications such as semiconductor lithography steppers have to withstand more than 10{sup 10} laser pulses without suffering from significant cumulative absorption increase due to color center formation. Lithography lasers are now approaching pulse durations of 10 ns and repetition rates of 1000 Hz, a domain unexplored in previous degradation studies. With the aid of an optical pulse-extension unit and a modified laser resonator, we measured absorptance and absorption changes in Suprasil 312 UV-grade fused silica calorimetrically at pulse lengths of 7 - 73 ns. At 100 mJ/cm{sup 2}, no degradation was detectable even after 500 000 pulses, but there was slight evidence of an absorption decrease due to laser cleaning. At 400 mJ/cm{sup 2}, both absorptance and degradation rate increased towards shorter pulses and hence higher intensities, but even over the full pulse-length range, the changes remained moderate. Furthermore, degradation at 300 Hz was lower than at 150 Hz, indicating that a simultaneous bleaching effect might be involved which favors future high-repetition rate applications.
- Research Organization:
- International Society for Optical Engineering, Washington, DC (United States)
- OSTI ID:
- 552254
- Report Number(s):
- CONF-961070-Vol.2966; TRN: 98:009063
- Resource Relation:
- Conference: 28. annual symposium on optical materials for high power lasers - Boulder damage symposium, Boulder, CO (United States), 7-9 Oct 1996; Other Information: PBD: [1997]; Related Information: Is Part Of Laser-induced damage in optical materials: 1996. Twenty-eighth annual Boulder damage symposium, proceedings; Bennett, H.E.; Guenther, A.H.; Kozlowski, M.R.; Newnam, B.E.; Soileau, M.J. [eds.]; PB: 686 p.
- Country of Publication:
- United States
- Language:
- English
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