Nanoscience and Nanotechnology 2014, 4(1): 1-6 DOI: 10.5923/j.nn.20140401.01 Characteristics of High-peed Cross-Gain Modulation in Quantum Dot Lasers Hussein H. Warid 1,* , Abdul Kareem H. Dagher 2 1 Physics department, College of Sciences, Thi-Qar University, Nasiriyah, Thi-Qar, Iraq 2 Physics Department, Education College, Al-Mustansiriyah University, Baghdad, Iraq Abstract In present work, we present simulation for the cross gain modulation (XGM) response of a quantum-dot laser (QD-LASER). an analytical model of XGM is derive by using four-level rate equation model (4LREM) under influence of external pumping in active region of (QD-LASER). In order to calculate the (XGM), (4LREM) modulated by add nonlinear self-gain saturation coefficient terms. Our date shows good agreement with other theoretical work.This serves to highlight how the modeling approach adopted can have a significant impact on the dynamic parameter values extracted from small signal measurements. Keywords Quantum Dot Laser, Cross Gain Modulation, Rate Equation Model 1. Introduction Wavelength converters are the key components in broadband networks. The next generation of high speed network and all it is functions need to transfer data by convert optical signals from one frequency to another to avoid wavelength-blocking and decrease the number of wavelength channels needed to operate a network. Wavelength conversion or frequency conversion mechanisms include cross-gain modulation (XGM), cross-phase modulation (XPM) and four-wave mixing (FWM) in semiconductor optical amplifiers (SOA). For high-speed uses, both XGM and XPM are limited by the carrier lifetime as they are dependent on interband carrier recombination and generation. According to our knowledge, there are several analytical models to calculate the XGM in semiconductor optical amplifier (SOA)[1]. In[2], by using two coupled rate equation model for carriers density and photon density an analytical model to calculate XGM response in semiconductor lasers is derive. The main goal of present work is investigation the modulation response in (QD-LASER). Due to gain saturation, high power signal at a is used to change the gain of a test laser by modulate the carrier density. The information transfer between pump wavelength and favorite test signal can be done by modulated favorite test signal in gain variation process. Coupled rate equations have been used widely to calculate the carrier dynamics and optical properties of QD-SOAs. * Corresponding author: hussien_hade@yahoo.com (Hussein H. Warid) Published online at http://journal.sapub.org/nn Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved Most published works that treat rate-equation models for these amplifiers consider only the electron dynamics. The hole dynamics is assumed to be so fast with respect to the electrons so that all the gain and spontaneous emission dynamical properties of the QDs are almost determined by the electron dynamics in conduction band. In the past, traditional modeling of bulk semiconductor lasers, involves describing the carrier (electron) and photon dynamics by a set of two coupled rate equations. Carriers are 3-D in nature and both equations are coupled through the processes of spontaneous and stimulated emission. Many of the features of all semiconductor lasers are well described by this approach, such as small signal response damping, turn on delay, relaxation oscillation under large signal modulation and pattern effects under high speed modulation. Based on rate equation model, there are several attempts to calculate the modulation response in semiconductor laser[3,4]. In[2], the last version for this subject is introduced. By using three-level rate equations model for (QW), an analytical model of the small-signal optical XGM theory is presented, take into account the escape/ relaxation lifetimes[5]. In present work, the modulation response of (QD-LASER), limited by the carrier lifetime as they are dependent on interband carrier recombination and generation in (QD-LASER). The paper is organized as follows. In Section II, we describe the four-level rate equations and an analytical model of the XGM in (QD-LASER). Results discussion in section III. 2. Four-Level Rate Equation Model and XGM Small-Signal Analysis With neglected the barrier dynamics, 4lrem describe the