Optical device including three-coupled quantum well structure

An optical device comprising:

• a lower reflection layer doped with a first conductive-type dopant;
• a first active layer on the lower reflection layer;
• an intermediate reflection layer on the first active layer and doped with a second conductive-type dopant that is electrically opposite to the first conductive-type dopant;
• a second active layer on the intermediate reflection layer;
• and
• an upper reflection layer on the second active layer and doped with the first conductive-type dopant,
• wherein at least one of the first and second active layers comprises a first outer barrier, a second outer barrier, and a first coupled quantum well inserted between the first outer barrier and the second outer barrier,
• the first coupled quantum well comprises a first quantum well layer, a second quantum well layer, a third quantum well layer, a first coupling barrier between the first quantum well layer and the second quantum well layer, and a second coupling barrier between the second quantum well layer and the third quantum well layer,
• thicknesses of the first quantum well layer and the third quantum well layer are less than a thickness of the second quantum well layer between the first quantum well layer and the second quantum well layer, and
• band gaps of the first quantum well layer and the third quantum well layer are larger than a band gap of the second quantum well layer.

An optical device, comprising:

• a first reflection layer;
• a first active layer on the first reflection layer, the first active layer including a first outer barrier, a second outer barrier, and a coupled quantum well between the first outer barrier and the second outer barrier;
• and
• a second reflection layer on the first active layer;
• the coupled quantum well including a first quantum well layer, a second quantum well layer, a third quantum well layer, a first coupling barrier between the first quantum well layer and the second quantum well layer, and a second coupling barrier between the second quantum well layer and the third quantum well layer,
• thicknesses of the first quantum well layer and the third quantum well layer being smaller than a thickness of the second quantum well layer between the first quantum well layer and the second quantum well layer, and
• band gaps of the first quantum well layer and the third quantum well layer being larger than a band gap of the second quantum well layer.