| 摘要 |
PURPOSE:To obtain stable oscillations, by forming a phase-shifting structure after making the presence of a diffraction grating produce an effective refraction index difference and making the probability of oscillating a single longitudinal mode approach one, thereby removing the diffraction grating where the electric field strength of light grows intense in the vicinity of its center part. CONSTITUTION:A clad layer 11 consists of a P-type InP layer; an active layer 12 consists of an InGaAsP layer; a waveguide layer 13 consist of an InGaAsP layer; and a clad layer 14 consists of InP substrate and then, a diffraction grating 15 has its cycle 4000Angstrom and a depth 2000Angstrom . Thus, a distributed feedback semiconductor laser device is composed of above elements. The effective refraction index which is susceptive to a laser beam is 3.306 at a region equipped with the diffraction grating 15 and is 3.300 at the region 16 without being equipped with the diffraction grating. Then, a phase-shifting structure is obtained by setting the length L of the region 16 which is free from the diffraction grating within the range of 27.1<=L<=54.2mum. Thus, the intensity of light distributes itself almost flat throughout the region 16 which is free from the diffraction grating. |
