Semiconductor optical amplifier

Abstract

The present invention provides a semiconductor optical amplifier capable of achieving high gain while reducing losses. [Solution] A semiconductor optical amplifier comprising a substrate having a silicon layer, and a gain portion formed of a III-V compound semiconductor having optical gain and bonded to the silicon layer, wherein the silicon layer has a waveguide, the gain portion has a mesa at a position overlapping the waveguide, the mesa protrudes in the direction opposite to the substrate and is located on the waveguide, and in the portion of the waveguide overlapping the mesa, the portion of the waveguide near the input end of the gain portion has a small cross-sectional area, and the portion of the waveguide near the output end of the gain portion has a large cross-sectional area.

Claims

1. A substrate having a silicon layer, It comprises a gain portion formed of a III-V compound semiconductor, having optical gain, and bonded to the silicon layer, The silicon layer has a waveguide, The gain section has a mesa at a position overlapping with the waveguide, The mesa protrudes in the direction opposite to the substrate and is located on the waveguide. A semiconductor optical amplifier in which, in the portion of the waveguide that overlaps with the mesa, the portion of the waveguide near the input terminal of the gain section has a small cross-sectional area, and the portion of the waveguide near the output terminal of the gain section has a large cross-sectional area.

2. The semiconductor optical amplifier according to claim 1, wherein in the portion of the waveguide that overlaps with the mesa, the portion of the waveguide closer to the input terminal of the gain section has a small width, and the portion of the waveguide closer to the output terminal of the gain section has a large width.

3. The semiconductor optical amplifier according to claim 1 or claim 2, wherein the width of the waveguide near the output end of the gain section is four times or more the width of the waveguide near the input end of the gain section.

4. The mesa has a first tapered portion at the end near the input end and the end near the output end. The semiconductor optical amplifier according to claim 1 or claim 2, wherein in the portion of the waveguide located between the two first tapered portions, the portion of the waveguide closer to the input end of the gain section has a large cross-sectional area, and the portion of the waveguide closer to the output end of the gain section has a small cross-sectional area.

5. The semiconductor optical amplifier according to claim 4, wherein the mesa has a constant width between the two first tapered portions along the direction of extension of the waveguide.

6. The semiconductor optical amplifier according to claim 5, wherein the width of the mesa is greater than the width of the portion of the waveguide closer to the input end of the gain section and smaller than the width of the portion of the waveguide closer to the output end of the gain section.

7. The gain section comprises a first semiconductor layer, an active layer, and a second semiconductor layer. The first semiconductor layer is bonded to the substrate and has a first conductivity type. The active layer and the second semiconductor layer are stacked sequentially on the first semiconductor layer. The semiconductor optical amplifier according to claim 1 or claim 2, wherein the second semiconductor layer forms the mesa and has a second conductivity type.

8. The first semiconductor layer has a second tapered portion, One of the two second tapered portions constitutes a part of the input end, One of the two second tapered portions constitutes a part of the output end. The mesa is located in the portion between the two second tapered portions. The semiconductor optical amplifier according to claim 7, wherein in the portion located between the two second tapered portions, the portion of the waveguide closer to the input end of the gain section has a small cross-sectional area, and the portion of the waveguide closer to the output end of the gain section has a large cross-sectional area.

9. The aforementioned silicon layer has a recess, The semiconductor optical amplifier according to claim 1 or claim 2, wherein the recess is located on both sides of the waveguide.

10. The semiconductor optical amplifier according to claim 1 or claim 2, wherein the width of the waveguide changes continuously or discontinuously along the direction of extension of the waveguide.

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