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Proceedings Paper

Analysis of thermally induced optical distortion in lens during focusing high-power CO2 laser beam
Author(s): Isamu Miyamoto; Hirokuni Nanba; Hiroshi Maruo
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Paper Abstract

Change of focus length due to CO2 laser beam absorption in ZnSe lens was analyzed by the thermal conduction theory and the physical optics. Temperature distribution was calculated in ZnSe lens where the thermal conductivity varies with temperature. Transient focus position was determined within an accuracy of by a diagnostic system where laser beam passing through a rotating slit probe moving along the beam axis is detected by a pyroelectric detector. Focus length was found to be shortened quickly in the initial 10-20 sec, reaching steady state in 60-90 sec in ZnSe lens of 2 inch-diameter. At absorbed power density wab<5 W/cm2, the focus shift is proportional to wab, and increases more rapidly at wab>S W/cm2 with accompanying aberration. The measured focus shift was found to agree well with calculated values. Effect of lens-to-holder contact on the transient focus shift are also discussed.

Paper Details

Date Published: 1 October 1990
PDF: 10 pages
Proc. SPIE 1276, CO2 Lasers and Applications II, (1 October 1990); doi: 10.1117/12.20537
Show Author Affiliations
Isamu Miyamoto, Osaka Univ. (Japan)
Hirokuni Nanba, Sumitomo Electric Industries (Japan)
Hiroshi Maruo, Osaka Univ. (Japan)

Published in SPIE Proceedings Vol. 1276:
CO2 Lasers and Applications II
Hans Opower, Editor(s)

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