| 摘要 |
PURPOSE:To realize lambda/4 phase shift without changing an optical guide mechanism by forming a rib-shaped diffraction grating having a discontinuous section along the direction of an optical guide, reducing the thickness of guide layers on both sides of the discontinuous section and shaping stepped sections. CONSTITUTION:A clad layer 2, an active layer 3 and a guide layer 4 are epitaxial-grown onto the main surface of a semiconductor substrate 1 in succession, and a diffraction grating 5 having width W1 and uniform pitches along the direction of an optical guide is shaped on the surface of the guide layer 4. A flat discontinuous section, a phase shift region 12, is formed at the center of the diffraction grating 5 and flat surfaces on both sides of the region 12. Flat sections 14b shaping stepped sections of half the height D of the diffraction grating 5 are formed on both sides of the phase shift region 12. A clad layer 6 and a cap layer 7 are shaped onto the whole surface of such a guide layer 4, and electrodes 9, 10 are formed onto both surfaces. |
