PURPOSE: To extend the life of a laser by internally containing a laser active substance which gradually reduces in a small signal gain during operation in a laser resonator, and decreasing the output coupling rate of the resonator as compared with the optimum output coupling rate corresponding to the initial small signal gain, thereby performing the increase in the minimum guaranteed output.
CONSTITUTION: A laser active substance with gradually decreases in the small signal gain is internally contained in a laser resonator which is composed of a laser tube 1, an output coupling mirror 3 and a fully reflecting mirror 3 during operation, and the output coupling rate of the resonator is decreased as compared with the optimum output coupling rate corresponding to the initial small signal gain. For example, in case of the external mirror type of a sealed tube CO2 laser unit, a partial reflecting mirror 4 and a high reflecting film 4' are formed on the surfaces of the mirrors 3, 3'. The output coupling rate is adjusted by controlling the reflectivity of the film 4.
IEHISA NOBUAKI
MATSUO KOUJI
FUKAYA KUNIAKI
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