International Journal of Optics and Applications. 2011; 1(1): 1-7 DOI: 10.5923/j.optics.20110101.01 Ultra High Speed Semiconductor Electrooptic Modulator Devices for Gigahertz Operation in Optical Communication Systems Abd El–Naser A. Mohamed, Mohamed A. Metawe'e, Ahmed Nabih Zaki Rashed * , Amira I. M. Bendary Electronics and Electrical Communications Engineering Department, Faculty of Electronic Engineering, Menouf, 32951, Menoufia University, Egypt Abstract The effects of electrodes geometry and temperature on high frequency radio frequency transmission charac- teristics are deeply investigated against semiconductor material based electro optic modulator devices such as aluminum gallium arsenide (AlGaAs) and optical waveguide parameters. On the other hand, we have developed the optimization of the electro-optic modulator parameters where the effective index plays an essential role in the evaluation of the bandwidth structure. Therefore, a theoretical analysis of the capacitance, the characteristic impedance and the effective index deter- mine how to increase the bandwidth. The effects of design parameters on the modulating voltage and optical bandwidth are also investigated for different materials based electro-optic modulators by using rigorous transmission modeling techniques. The low-loss wide-bandwidth capability of optoelectronic systems makes them attractive for the transmission and process- ing of microwave signals, while the development of high capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. Keywords Electrooptic Modulator, Semiconductor Material, Optical Bandwidth, High Transmission Performance 1. Introduction Present communication technology relies on fiber-optic systems which include light sources such as a laser, optical fiber, integrated optical components such as modulators and switches, and optical detectors. The lasers and detectors are fabricated using semiconductor materials, and the integrated optical components are generally fabricated using elec- trooptic single crystal materials such as lithium niobate (LiNbO 3 ). Among the integrated optical components, the contribution from electrooptic modulators using LiNbO 3 waveguide structures has been significant in the last several decades due to their high speed and chirp-free nature[1]. The essential requirements for efficient electrooptic modulation are low half-wave(switching) voltage and broad 3-dB bandwidth. The optical modulator is a key component for photonics. Optical fiber communications, microwave photonics, instrumentation, and optical signals processing all require optical modulators. Several different technology platforms can be used for the realization of optical modula- tors. Of these, LiNbO 3 based ferroelectric electrooptic modu- * Corresponding author: ahmed_733@yahoo.com (Ahmed Nabih Zaki Rashed) Published online at http://journal.sapub.org/optics Copyright © 2011 Scientific & Academic Publishing. All Rights Reserved lators provide the most mature technology. Electro-optic polymers and compound semiconductors are also attractive technologies for optical modulators. High-speed integrated electro-optic modulators and switches are the basic building blocks of modern wideband optical communications systems and represent the future trend in ultra-fast signal processing technology. As a result, a great deal of research effort has been devoted to developing low-loss, efficient and broad- band modulators in which the radio frequency signal is used to modulate the optical carrier frequency[2]. Most of the work done in the area of designing electrooptic modulators has been strongly focused on using LiNbO 3 [3]. Interest in research in this field has arisen as lithium niobate devices have a number of advantages over others[4], including large electro-optic coefficients, low drive voltage, low bias drift, zero or adjustable frequency chirp, and the facility for broadband modulation with moderate optical and insertion losses and good linearity . However, on the other hand, LiNbO 3 devices cannot be integrated with devices fabricated using other material systems such as semiconductors and as a result they are best suited to external modulation applications. However, with the recent developments in semiconductor technology, modulators based on semiconductor materials have been receiving increasing attention. In particular, Al- GaAs/GaAs material offers the advantage of technological maturity and potential monolithic integration with other