Accession Number:

ADA564804

Title:

High Power Optical Coatings by Atomic Layer Deposition and Signatures of Laser-Induced Damage

Descriptive Note:

Final rept. 1 Aug 2009-31 Jul 2012

Corporate Author:

MINNESOTA UNIV MINNEAPOLIS OFFICE SPONSORED PROJECTS ADMINISTRATION

Personal Author(s):

• Talghader, Joseph J.

Report Date:

2012-08-28

Pagination or Media Count:

30.0

Abstract:

This report describes an investigation of the properties of optical coating oxides deposited by atomic layer deposition. Specifically, two oxides were chosen as indicative of the group as a whole aluminum oxide Al2O3 and hafnium oxide HfO2. Uniform films and nanolaminates films with inserted layers of alternate materials were deposited and tested for thermal conductivity. absorption, and laser damage threshold, among other properties. Significant effort went into the analysis of the thermal conductivities of the films since thermal breakdown is particularly relevant to directed energy applications. The interface thermal resistance in hafnia-alumina nanolaminates is very low and does not dominate the film thermal conductivity. The degree of crystallinity of these films appears to have a much larger effect on thermal conductivity than that of interface density. Cryogenic measurements show partial agreement with both the minimum thermal conductivity model for disordered solids and the diffuse mismatch model of interface resistance. Absorption measurements show results less than or near 1ppm, which matches or exceeds the performance of the best films deposited by other methods.

Descriptors:

• *OPTICAL COATINGS
• ALUMINUM OXIDES
• CRYOGENICS
• DIFFUSION
• HAFNIUM COMPOUNDS
• HIGH POWER
• LASER DAMAGE
• ORDER DISORDER TRANSFORMATIONS
• THERMAL CONDUCTIVITY
• THERMAL RESISTANCE
• THRESHOLD EFFECTS

Subject Categories:

• Coatings, Colorants and Finishes

Distribution Statement:

APPROVED FOR PUBLIC RELEASE