| abstract |
The presence or absence and the intensity of refractive index distribution are easily controlled with high reproducibility without depending on the fabricating process accuracy. InGaAs well layers ( 14 a ) and ( 14 b ), which have a narrow bandgap and a high refractive index, are enclosed by a lower barrier layer ( 13 ), an intermediate barrier layer ( 15 ), an upper barrier layer ( 16 ) and a buried layer ( 18 ) of GaAsN-based materials of a wide bandgap. Then, by adjusting the nitrogen crystal mixture ratio of the GaAsN-based materials that constitute the barrier layers ( 13 ), ( 15 ) and ( 16 ) and the buried layer ( 18 ), the presence or absence and the intensity of the refractive index distribution are controlled. Thus, the refractive index distribution is easily controlled with high reproducibility without considering the configuration of a diffraction grating ( 17 ), a refractive index balance with respect to the buried layer ( 18 ) and so on, i.e., without depending on the fabricating process accuracy. |