| 摘要 |
PURPOSE:To increase a necessary light output and reduce the noise level without using an optical isolator, by providing a waveguide layer at the lower part of an active layer of a semiconductor laser with a diffraction grating to give the reflectivity a fluctuation of quater-wavelength period at a center frequency of a light to be amplified in the semiconductor laser. CONSTITUTION:An input end of a semiconductor laser is formed by a creep end 1 or a non-reflecting film 2, and an output end is formed by a non-reflecting film 2. A bias level is so set that a self oscillation does not generate. A waveguide layer 4 at the lower part of an active layer 3 is provided with a diffraction grating 5 to give the reflectivity a fluctuation with a period of a quater of wavelength lambda0, at a center frequency of a light to be amplified in the semiconductor laser. As the period is lambda0/4, a feedback light is canceled in the diffraction grating, and incident light is restrained from reflecting and travelling backward. Accordingly, the unilateral amplification effect is generated, and the output is almost doubled. Thereby, an optical isolator of high cost is not required. Further, as the result of large light output, the noise generation is little and a low noise operation is enabled. |
