在飞秒太瓦激光装置中，高效率的压缩光栅是获得高峰值功率飞秒激光输出的最重要光学元件之一。虽然光栅安装在无油的真空室内，但当光栅受到强激光的辐照时，真空中残存的气态有机物会被碳化并沉积在光栅表面，使得光栅受到“污染”，衍射效率大大降低。激光辐照累积的热量会导致光栅结构发生变化，甚至会造成光栅的永久损伤。为此发展了用等离子体来清洗光栅表面污染层的方法，实验结果表明该方法非常有效地清洗了光栅表面的污染，提高了衍射效率并避免了光栅的损伤。该方法简单，易于操作，可以安装在压缩光栅真空室上，在不影响真空室里面的光学元件情况下可以实现实时清洗。

The diffraction efficiency of compression gratings in chirped-pulse amplification is very crucial to obtain terawatt femtosecond laser. Although the gratings are located in vacuum chamber with oil free, the gratings illuminated by laser beam are still subjected to carbon contamination in the vacuum condition, and results in degradation of diffraction efficiency. Moreover, additional energy deposition on the surface of grating will lead to irreversible changes of the grating structure or even catastrophic damage. A plasma cleaning technique is introduced to realize cleaning of carbon layer on the grating. The diffraction efficiency of grating is obviously improved after cleaning. It is demonstrated that the plasma cleaning is an effective on-line technique to repeatedly recover the high efficiency of compression gratings before damage occurs due to excessive carbon deposition.