Nonlinear effects in blue-shift waveguide EAM's

Abstract

To exploit the vast bandwidth of optical communication systems for high bit-rate long-haul transmission, external modulators show a better system performance than directly modulated lasers. One of the main advantages of electroabsorption modulators (EAM's) compared with Mach–Zehnder modulators is the possibility to integrate the modulator with a laser having the same active layer. This reduces processing complexity and system costs. Usually the quantum confined Stark effect results in a red shift of the absorption, which 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 structures suffer from the drawback that saturation effects may occur for higher optical power as these devices absorb the optical power at low applied bias. The aim of this paper is to investigate the influence of nonlinear saturation effects like carrier accumulation, Burnstein–Moss-effect and carrier screening.