SEDL / STP / STP911-EB / STP28959S

Strehl Ratio Measurements of Laser Damaged Plastics

Mullins, BW
United States Air Force Academy, Colorado Springs, Colorado

Richert, BA
United States Air Force Academy, Colorado Springs, Colorado

Pages: 4    Published: Jan 1985

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Abstract

Plexiglass G, manufactured by Rohm Haas, was irradiated by 10 nsec pulses from a Nd-YAG laser ranging in energy from 0.80 to 1.01 mJ/pulse. Aligned colinearly with the Nd-YAG pulse was a cw HeNe laser beam that measured changes in the transmission characteristics of the plastics. These transmission measurements enabled the Strehl Ratio, S, of the laser induced damage site to be calculated. When S < 0.995 there is a 92% probability of causing permanent damage. Conversely, when S > 0.995 there is a 94% chance of not causing permanent damage to the plastic. These probabilities were independent of laser pulse energies. Evaluation of the resulting diffraction patterns from the permanent damage sites indicates an ∼ 20μm diameter of the optical scattering center in the plastic. These damage sites cause an rms wavefront distortion ranging from 0.009λ to 0.0301λ at the HeNe wavelength.