Reflective semiconductor optical amplifier (R-SOA) with dual buried heterostructure
View Patent ↗Provided are a reflective semiconductor optical amplifier (R-SOA) and a superluminescent diode (SLD). The R-SOA includes: a substrate; an optical waveguide including a lower clad layer, an active layer independent of the polarization of light, and an upper clad layer sequentially stacked on the substrate, the optical waveguide comprising linear, curved, and tapered waveguide areas; and a current blocking layer formed around the optical waveguide to block a flow of current out of the active layer, wherein the linear and curved waveguide areas have a single buried hetero (BH) structure, and the tapered waveguide area has a dual BH structure.
1. An R-SOA (reflective semiconductor optical amplifier) comprising:
a substrate;
an optical waveguide comprising a lower clad layer, an active layer independent of the polarization of light, and an upper clad layer sequentially stacked on the substrate, the optical waveguide comprising linear, curved, and tapered waveguide areas, the tapered waveguide area includes the active layer or a tapered waveguide; and
first and second current blocking layers formed around the optical waveguide to block a flow of current out of the active layer,
wherein the first current blocking layers are positioned at left and right sides of at least one of the tapered waveguide and the active layer of the tapered waveguide area, forming a first BH (buried hetero) structure, and
wherein the second current blocking layers are positioned at leftmost and rightmost sides of the first current blocking layers, forming a second BH structure.
2. The R-SOA of claim 1 , wherein a passive waveguide is disposed under the active layer and the passive waveguide is tapered under the curved waveguide area, and has a constant width in the tapered waveguide area.
3. The R-SOA of claim 1 , wherein the tapered waveguide area includes the tapered waveguide, and the active layer is butt-coupled to the tapered waveguide.
4. The R-SOA of claim 1 , wherein the tapered waveguide area includes the active layer, and the active layer is formed of a same material in the linear, curved, and tapered waveguide areas.
5. The R-SOA of claim 1 , wherein p-InP, n-InP, and p-InP layers are formed around the linear waveguide area as the second current blocking layers.
6. The R-SOA of claim 1 , wherein p-InP and n-InP layers are formed around the tapered waveguide area as the first current blocking layers, and p-InP, n-InP, and p-InP layers are formed around the tapered waveguide area as the second current blocking layers.
7. The R-SOA of claim 1 , further comprising a trench formed by removing portions of the first and second current blocking layers and the substrate.
8. The R-SOA of claim 1 , wherein the active layer in the linear and curved waveguide areas and the second current blocking layers adjacent to the active layer in the linear and curved waveguide areas collectively form a third BH structure, such that the second current blocking layers are positioned at left and right sides of the active layer.
9. The R-SOA of claim 1 , wherein the active layer has a bulk structure.
10. The R-SOA of claim 3 , wherein the tapered waveguide is formed of InGaAsP.
11. The R-SOA of claim 2 , wherein the first current blocking layers are disposed on an upper side of the passive waveguide and the second current blocking layers are disposed at left and right sides of the passive waveguide.