| 摘要 |
PURPOSE: To improve amplification efficiency by forming an optical wave guide path where rare earth elements are added and the optical wave guide path where rare earth elements are not added, on different planes. CONSTITUTION: An optical wave guide path core part 1c for incidence of an exciting light and an optical wave guide path core part 1d for incidence of a signal light are made on a buffer layer 1b. Active elements such as Er, etc., are not added to these guide path cores 1c and 1d. And, the guide paths 1c and 1d are stopped with a flattened lower-layer clad layer 1e. An optical wave guide path core 1f where rare earth elements are added is made on the lower- layer clad layer 1e. This way, rare earth elements are not added to the region 11d which propagates only the exciting light of the lower-layer part and the region 1m which propagates only the signal light, and rare earth elements are added to the region 1n which propagates the superposed light of the amplified signal light 1ii and the exciting light which is weakened, being absorbed, so the signal light ceases to be attenuated with rare earth elements, and amplification efficiency improves. |
