Semiconductor optical amplifier

Abstract

An optical amplifier with a semiconductor body includes a layer structure grown on a substrate, with an active layer between two cladding layers, and a strip-shaped amplification region bounded by two end faces of low reflection which form the input and output faces for the radiation to be amplified. The active layer has a number of quantum well (QW) layers with direct band transition, and separated by barrier layers of a different semiconductor material, a first portion of the QW layers being under tensile stress. Another portion of the layers forming part of the active layer is under compressive stress. Owing to the compressive stress present locally in the amplification region, the TE-mode is more strongly amplified there than the TM-mode, while in the tensile portion of the amplification region the TM-mode is more strongly amplified than the TE-mode. This results in a polarization-insensitive amplifier with higher stress and thus with a large amplification at a relatively low current. In one embodiment, both portions of QW layers are within one stack of layers containing the amplification region. In another embodiment both portions are positioned in different stacks that are located next to each other each adjoining a different end zone of the amplification region. In the latter, independent adjustment of the TE and TM amplification profiles is possible.