| 摘要 |
A nonreflective film includes films having refractive indices higher than 1 and a high-refractive index film (first film, third film, fifth film) and a low-refractive index film (second film, fourth film, sixth film, seventh film) respectively having refractive indices higher and lower than the square root of an effective refractive index of a semiconductor laser. The films have least three different compositions. Each film has a single composition. The films bring a real part and an imaginary part of an amplitude reflectance to zero, as a whole. Therefore, a semiconductor optical device with an improved degree of freedom in design of the nonreflective film is provided, even when a total thickness of the films is different from one quarter wavelength of the incident light.
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