GAIN SATURATION IN TRAVELING-WAVE SEMICONDUCTOR OPTICAL AMPLIFIERS

The gain saturation behavior of semiconductor traveling-wave optical a mplifiers has been analyzed using a model that includes the specific d ependence of gain on carrier concentration. Under the condition of a s pecific gain at a particular current, it is found that the saturation power strongly depends on the choice between quantum well (QW) or bulk amplifying medium but weakly on the detailed design of the device suc h as the number of QW's or the thickness of the hulk layer, The higher saturation power of the QW-based amplifier is caused by its logarithm ic gain-current relation rather than its low optical confinement facto r. Also, when the unsaturated device gain is specified, the designed s aturation power can be obtained with the lowest drive current by using the highest optical confinement.