Non-uniform thickness or bandgap superlattice betweeen cladding layer and multi-quantum well structure of pin optical waveguide

摘要

In the structure of the device of the invention, a supper- lattice buffer layer is formed between the undoped layer and doped layers. This super-lattice buffer layer serves as a carrier-piling up layer in place of the undoped layer in the conventional device. Thus, the amounts of the piled-up carriers in the undoped layer can be greatly reduced and hence no band filling effect occurs in the undoped layer. Consequently, an optical device having a flat frequency characteristic can be produced without losing its modulating characteristic.