Correlating laser damage tests.

This paper reports on efforts to correlate two commercially oriented laser damage tests. The two test facilities are located at Hughes Aircraft Co. and Montana Laser Optics*. A variety of coated laser optics have been tested in different test conditions and the damage levels compared. The test parameters varied were transverse modal content, spot size, sample conditioning history and, to a lesser degree, pulse width. The accumulated results were correlated by ascertaining the existence of a high probability functional relationship (linear fit) between pairs of damage levels for the same optics in different test conditions. A strong correlation was found between samples tested with the same irradiance history, regardless of the modal content and pulse width. Comparisons of the samples of different irradiance conditioning history were found not to correlate in general.

1.06-microm laser damage of thin film optical coatings: a round-robin experiment involving various pulse lengths and beam diameters.

A number of commercially available optical coatings, both antireflective and high reflective, have been tested for their laser-induced damage threshold, involving a total of eight different laboratories. The results obtained and the experimental methods used at these laboratories were discussed among the participants in this round robin at a minisymposium held at Balzers, Liechtenstein, 9-10 Dec. 1982. A final report of the round robin and a summary of the conclusions drawn at that symposium are presented.

Measurement of optical coupling coefficients based on thermal expansion.

A fundamentally new method for measuring optical coupling coefficients is described. A sample of a particular shape is subjected to a fixed tensile load and heated with pulsed optical radiation. The resulting peak tensile relaxation is proportional to the total absorbed energy; evolution of the coupling coefficient may thus be observed. A prototype system was constructed, and coupling coefficients were measured as a function of incident energy for CO(2) laser pulses on bare and painted aluminum surfaces. With a sample of known absorptance and thermal properties, the system functions as a sensitive, fast-response, absolute-energy-measurement device.