Nonlinear effects in blue-shift waveguide EAM's

To exploit the vast bandwidth of optical communication systems for high bit -rate long-haul transmission, external modulators show a better system perf ormance than directly modulated lasers. One of the main advantages of elect roabsorption modulators (EAM's) compared with Mach-Zehnder modulators is th e possibility to integrate the modulator with a laser having the same activ e layer. This reduces processing complexity and system costs. Usually the q uantum confined Stark effect results in a red shift of the absorption, whic h leads to a small gain due to a detuned operation of the integrated laser. In contrast, blue shift structures have been proposed for these integrated devices as they show both good laser and modulator properties. These struc tures suffer from the drawback that saturation effects may occur for higher optical power as these devices absorb the optical power at low applied bia s. The aim of this paper is to investigate the influence of nonlinear satur ation effects like carrier accumulation, Burnstein Moss-effect and carrier screening.