CO_2レーザ照射によるZnSeレンズの温度分布 : 高パワーレーザによるレンズの熱誘起光学ひずみ(第1報)

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Temperature distribution in edge cooled ZnSe lens was numerically analyzed during focusing high power CO_2 laser beam where thermal conductivity K varies with temperature T, K=K(T). Simple analytical solutions at steady state were also derived for different laser modes assuming K is constant. Results obtained are summarized as follows ;(1) Assuming K=const, the accuracy of calculated temperature decreases with increasing steady temperature at the center, T_<sc>, which becomes 1.5 times as high as the exact value at T_<sc>=100 C.(2) Steady temperature gradient calculated with K=const is proportional to r in laser irradiation region for a circular uniform beam of radius a, and is given by a curve having a peak at r=1.12a for Gaussian beam (a=1/e-radius), of whidh peak is 64% of that of the circular beam.(3) Simple equations to provide accurate steady temperature distribution and gradient were derived ; T_k(r)=T(r)/(1-mT_<sc>) and (dT/dr)_k=(dT/dr)/(1-mT_<sc>), where T(r), T_<sc> and dT/dr are temperatures at r=r and r=0 and temperature gradient at steady state for K=const, respectively.(4) The temperature rise of ZnSe lens was measured during focusing CO_2 laser beam by a fluoroptic thermometry, and was found to agree well with calculated values.
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1992-05-05