US Patent 7288783 - Quantum dots formed on a curved surface

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In optical communication systems a wide band of wavelengths introduce differences in polarization which can limit optical amplification. The inventor behind this patent from Fujitsu Ltd. realized that formation of quantum dots on a curved surface can provide optical amplification independent in polarization allowing for use in wideband applications . Claim 1 reads:

1. An optical semiconductor device comprising: an active layer including a plurality of quantum dots; a lower clad layer formed below the active layer; and an upper clad layer formed above the active layer, said plurality of quantum dots being formed on a plurality of surfaces whose normal directions are different from each other, wherein each surface has a normal direction different from a normal direction of any one of the other surfaces, and said plurality of quantum dots are formed on each surface, respectively, the quantum dots are formed on a curved surface.