| 摘要 |
PURPOSE:To perform the single wavelength oscillation easily by a method wherein a resonator is formed by the optical feedback using a diffraction grating to make the refractance percentage at both ends of distribution feedback type semiconductor with 1/4 wavelength shift structure asymmetrical while successively changing the thickness of active layer or guidewave layer in the direction of resonator. CONSTITUTION:An active layer 12, an optical waveguide layer 13 with a diffraction grating including 1/4 wavelength shifting structure are clad with layers 11 and 14. The laser oscillation characteristics of even distribution feedback structure in length L and grating cycle A can be analyzed while the laser with successively changing film thickness is regarded as an even distribution feedback element group of N each, e.g., when the resonator length of 300mum, the coupling coefficient of diffraction grating of 2, the reflectance percentage at laser ends of 90%, 1% and the difference in active layer thickness at both ends of resonator of DELTAd are assumed, if DELTAd =200-300Angstrom , the propagation constant fluctuates specially and the coincidence requirement between the phase at the end of reflectance percentage of 90 % and the phase inlambda/4 shift is relieved while increasing the probability of single axis mode oscillation. In such a constitotion, similar effect can be gained by changing the thickness of optical waveguide layer or active layer and optical waveguide layer in the direction of resonator. |
