| 摘要 |
PURPOSE:To obtain a constant gain with respect to injected light without depending upon the state of polarization of the light by mutually crossing the thickness directions of active layers in two semiconductor laser elements arranged onto the same optical path in a cascade manner at right angles to the deflection of light on the optical path. CONSTITUTION:Light propagated in a single-mode optical fiber 1 is injected to an active layer 4 in a light amplifier 3 through a SELFOC lens 2, and amplified respectively to TE waves and TM waves only by gains GTE1, GTM1 and output. Amplified light is injected to an active layer 7 in a light amplifier 6 through a lens 5'', and amplified respectively only by gains GTE2, GTM2 and output. When an optical isolator 10 having no polarized wave dependency is inserted between the light amplifiers 3, 6, light returns to the light amplifier 3 at a pre-stage owing to the incompleteness of a nonreflective film, thus preventing the generation of the increase of noises and the saturation of gains. When an optical filter is used at an outgoing end, the quantity of spontaneous emission light of the light amplifier 3 is reduced. |
