Abstract: An HF-excited gas laser has a laser tube of ceramic material containing a laser gas, and the tube includes a chemical component which will preclude passage therethrough of secondary radiation of a wavelength within a proscribed range which would interact with the material of the laser tube to create defects therein. The chemical component to prevent damage to the laser tube may be provided as a layer on its inside surface which is essentially impermeable to and/or reflects the secondary radiation back into the lasing gas. Alternatively, the material of the laser tube may incorporate the chemical component, preferably over the portion of the wall adjacent its inner surface.