Laser Window Surface Finishing and Coating Science
Abstract
The objectives and the progress achieved in a program to study the surface finishing and coating of laser windows for high energy laser applications in the 10.6 micrometers 5.3 micrometers and 3.8 micrometers wavelength regions are reported. Recent chemical-mechanical optical polishing procedures use 1,2-propanediol, whose surface etch rate appears to match the rate of formation of damaged surface layers produced during polishing. Polycrystalline windows approximately 5 cm in diameter and 1 cm thick have been polished flat to 1/4 fringe in the visible with faces parallel to 2 arc sec, total optical absorption loss at 10.6 micrometers of 0.0007 for a 1 cm thick piece was measured after polishing. Recent coating efforts have placed emphasis on the use of three layer antireflection coatings produced in ultrahigh vacuum in an attempt to remove the absorption limitation of >0.1% per surface for the two layer coatings produced previously which have prevented the achievement of a program goal of <0. 1% coating loss per surface at 10.6 micrometers. With the new three layer coating designs it was possible to achieve coating absorption losses as low as 0.05% per surface for ZnSe/ThF4/ZnSe designs. The rather high values of absorption index (K=.003) for ThF4 films used at 10.6 micrometers can now be incorporated in our new designs and we can still achieve coatings with less than 0.1% absorption losses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1976
- Accession Number
- ADA022684
Entities
People
- A. I. Braunstein
- C. R. Giuliano
- J. E. Rudisill
- M. Braunnstein
- S. D. Allen
Organizations
- HRL Laboratories