| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical detector which performs optical wave branching and detecting operations at low cost and with compact arrangement. SOLUTION: A mesa-shaped, stripe-like PIN photodiode structure having a multi-quantum well layer 10 as a light-absorbing layer is formed on a substrate 15 as continuous sections A, B and C. By having the thickness of the multi-quantum well layer 10 varied in various sections, the section C can absorb and detect a incident multiplexed into a light of wavelengthsλ1,λ2 andλ3 having the wavelengthλ3, so that the section B can absorb and detect part of the incident light having the wavelengthλ2, and the section A can absorb and detect the part of the incident light having the wavelengthλ1.
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