Accession Number:

ADA160887

Title:

Investigate Laser Induced Damage in Optical Coatings Using Time Resolved Raman Spectroscopy.

Descriptive Note:

Final rept. Jan-Nov 84,

Corporate Author:

BATTELLE MEMORIAL INST RICHLAND WASH PACIFIC NORTHWEST LABS

Personal Author(s):

Report Date:

1985-08-01

Pagination or Media Count:

41.0

Abstract:

Raman spectroscopy is shown to be a viable and rapid technique for characterization of laser induced damage in thin dielectric coatings of fused silica substrates. Unequivocal identification of crystalline and amorphous phases can be discerned from measured vibrational spectra. A two laser damage-probe technique has been developed for in situ analysis of laser coatings. Raman measurements made at long times following pulsed laser damage serve to characterize the equilibrium damage state and can be used to spatially profile the damage zone. Time resolved measurements acquired within nanoseconds following laser induced damage to optical coatings are studied by these and related Raman experiments from which mechanistic information can also be inferred. The primary mechanism of failure in titanium dioxide TiO2 coatings results from crystalline phase changes induced thermally or by multiphoton excitation processes. A similiar failure mode is predicted for other oxidic coatings such as zirconium dioxide ZrO2 which can exist in different room temperature stable phases. Keywords Laser Damage Mechanisms Time Resolved Raman Spectroscopy Molecular Vibrational Studies Laser Heating Phase Transformations Titanium Dioxide Optical Coatings.

Subject Categories:

  • Radiation and Nuclear Chemistry
  • Coatings, Colorants and Finishes
  • Optics
  • Solid State Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE