| 摘要 |
PROBLEM TO BE SOLVED: To facilitate alignment work of the propagating direction of light in a window material with the C-axis direction of the window material. SOLUTION: In a sapphire window material, the window material of a hermetically sealed vessel 5 which holds a semiconductor laser element 4 is formed of a sapphire. When the window material 1 is fixed to the hermetically sealed vessel, the C-axis direction of the window material is set obliquely at the angle of a formula (1)α=sin<SP>-1</SP>(sinθ/n(λ)) to a normal of an optical surface of the window material, whereθis the oblique angle of the window material in a direction perpendicular to an optical path direction of an emitting light from the semiconductor laser element, and n(λ) is the refractive index of the window material to the wavelengthλof the emitted light, and a marking is formed on the window material so that the rear surface and the front surface of the window material in a direction of the optical path become different appearances. COPYRIGHT: (C)2005,JPO&NCIPI
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