| 摘要 |
PROBLEM TO BE SOLVED: To enable optical coupling of optical devices with different spot sizes after reducing polarization dependency. SOLUTION: A lower clad layer 101a is formed on the surface of a substrate 101 consisting of n-type InP by processing the surface into a stripe shape. A taper core 102 (spot size conversion region) consisting of InGaAsP, which is compound semiconductor, and an active region core 103 are formed on the surface. The density of n-type impurity in the substrate 101 (lower clad layer 101a) is made, for example, 1×1018 cm-3 and less than 2×1018 cm-3.
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