| 摘要 |
PURPOSE:To protect optical parts from contamination and thus elongate the lifetime of optical parts by arranging a pair of perforated windows inside optical parts forming a resonator, and delivering clean gas between the windows and the optical parts. CONSTITUTION:A resonator includes a half-mirror 24 and a full mirror 25. Windows 26, each having holes, are placed inside optical parts in the resonator. The window is made of an opaque material such as artificial lime, calcium fluoride, or magnesium fluoride. Clean gas 28 is supplied between the windows and optical parts from a gas cleaner 27, and spouted through the holes. Since clean gas is filled between the windows and optical parts, contaminant is prevented from entering. In addition, the spouting of gas substantially prevents contaminant or undesired gas from reaching the optical parts. Therefore, degradation of optical parts is prevented. |
