| 摘要 |
PURPOSE:To obtain the high-reliability optical modulator which is durable to long-time operation by increasing the light absorptivity of an absorption layer gradually in the traveling direction of light and nearly uniforming the power of light absorbed in each area of the absorption layer. CONSTITUTION:The light absorptivity of the absorption layer 22 is increased in the traveling direction of light to nearly uniform the power of light absorbed in each area of the absorption layer 22. For example, when the thickness of the absorption layer 22 is increased gradually (t2 t1) in the traveling direction of the light, the light incident on the optical modulator decreases in power as it travels in the absorption layer 22, but the power of light absorbed in areas 22a and 22b of the absorption layer 22 can nearly be uniformed. Namely, large-power light is not absorbed in the area close to the incidence end surface of the absorption layer 22 more in the area close to the projection end surface and, therefore, only any area does not deteriorate early. Consequently, the high-reliability optical modulator which has long life and is durable to long-time operation can be obtained. |
