| 摘要 |
PROBLEM TO BE SOLVED: To provide a ridge type semiconductor optical amplifier which enables a switching operation with high speed and is low in cost. SOLUTION: After a lower clad layer 21, an active layer 22, an upper clad layer 23 and a contact layer 24 are successively formed on a semiconductor substrate 20, the contact layer 24 and the upper clad layer 23 are processed so as to form approximately a rectangular shape. By doing this, since crystal growth is necessitated just once, the production cost can be reduced when forming an SiO2 layer 26 and a polymer layer 27. The forming process of the SiO2 layer 26 and the polymer layer 27 are inexpensive processes compared with the process of crystal growth. And, by using the SiO2 film 26 having a low dielectric constant and a polymer layer 27, a parasitic capacitance can be reduced. As a result, a high-speed optical switching operation can be performed. Moreover, an etching is carried out so that the widths of the upper clad layer 23 and the contact layer 24 become narrower as tapered at the incident and exit side of the signal light. Consequently, the device can be highly efficiently connected with the optical fibers at both sides faces.
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