| 摘要 |
PURPOSE:To get a laser to operate at a stable single longitudinal mode by structuring a part of a wave guide structure whose equivalent refractive index is changing relatively with the other part so that a threshold gain difference between one mode and the other mode which are wanted to be oscillated is made large. CONSTITUTION:A secondary diffraction grating 12 is formed on an n-type InP substrate 11. On the secondary diffraction grating 12, an n-type GaInAsP optical waveguide layer 13, an undoped GaInAsP active layer 14, a p-type GaInAsP anti-meltback layer 15, a p-type InP clad layer 16 and a p<+>-type GaInAsP ohmic contact layer 17 are piled up in order. After that, a mesa.stripe section is formed by etching with the thickness of the waveguide structure uniform while the width of the central part is made narrow, forming a phase shift section 30. Then, around the phase shift section 30, a p-type InP layer 18, an n-type InP layer 19 and an undoped GaInAsP gap layer 20 are deposited in series and then are buried. By this method, a laser can be operated at a stable single longitudinal mode with the TM mode well under control. |
