Damage in the germanium output mirror of a TEA CO2 laser shows a periodicity of 10.6 μm, the laser wavelength. A mechanism is proposed in which scattered and cavity radiation interfere. An interference mechanism is confirmed by experiments outside of the laser cavity. Periodic damage is obtained in thin films irradiated at angles other than the normal where the fringe spacing is modified.

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Considerable interest centres around the use of germanium as a reflector material in high-power carbon-dioxide lasers. An important problem is the damage caused to the mirror surface as the result of the dynamic development of imperfections. This damage may be caused by an interference process which has been described previously. A characteristic of the damage which occurs is the melting of the germanium followed by resolidification. The authors describe a certain type of melting pattern which depends upon density differences between the liquid and solid phases. The experimental phenomenon is first described with reference to germanium laser mirror damage and this is followed by a theoretical model of the resolidification of molten regions where a density difference occurs between the solid and liquid phases, as in paraffin wax for example.

Laser-induced contamination (LIC) can be a major concern of using UV laser systems. Surface contamination occurs via interactions between the UV laser and particulates, water vapor condensate, organics, and airborne molecular contaminates (AMC) from the environment or outgassing from system materials. A brief review of contamination of optics will lead into present results from long-term 355 nm quasi-CW laser transmission experiments at Edmund Optics. Time lapse microscopy was used to monitor nucleation and growth of surface contaminants. Laser burn boxes were constructed for use as a controlled UV LIC testbed; experimental results are presented on transmission losses for various material preparation methods.