| 摘要 |
PROBLEM TO BE SOLVED: To prevent, for example, an optical element and a coating film from being damaged by applying a beam where the pulse width of an excimer laser is longer than a specific value. SOLUTION: A beam where the pulse width of an excimer laser 1 is longer than 100 ns is applied. The oscillation life of the laser itself is extended. For example, the spiker/sustainer vibrating method is known as the method for extending pulses, and a pulse width exceeding 1μs is achieved. More specifically, the pulse width can be drastically extended without using any additional optical system such as an optical system for splitting an optical path, thus extending the pulse width at least by 100 times as compared with a normal pulse width of 10 ns. Therefore, an energy density per unit time becomes much smaller, namely 1/10 or less, thus preventing an optical element and a coating film from being damaged. The electron density of discharge can be controlled by electron beams for extending life or the plasma cathode ionization method can be utilized.
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