Journal of Applied Sciences Research, 5(10): 1692-1697, 2009 © 2009, INSInet Publication Corresponding Author: Osama Mahran, Faculty of Science, University of Alexandria, Alexandria, Egypt, E-mail:o_mahran2003@yahoo.com 1692 2 3 Temperature Effect on the Emission Cross Section of Er in Al O Fiber Amplifier 3+ Osama Mahran, Mohammed Salah Helmy and Mourad Abd El Hai Faculty of Science, University of Alexandria, Alexandria, Egypt Abstract: The study of temperature dependent emission cross section, gain coefficient and gain of the Er- 2 3 doped Al O fiber amplifier in the range 290 to 310 K is carried out. McCumber procedure is used to predict the emission cross-section spectrum of the 1.5 ì m transition of Er-doped glass fibers from the transition's measured absorption spectrum. The gain coefficient and gain of the amplifier are calculated using the transition rate equations at the pump wavelength 980 nm. It is found that emission cross section, gain coefficient and the gain of the amplifier increase with temperature in the amplifier window 1.53 ì m. Key words: Optical Amplifier, Temperature Effect, Erbium, Emission Cross Section. INTRODUCTION Accurate modeling of Er-doped fiber amplifiers (EDFAs) and waveguide amplifiers for design and performance analysis purposes requires the knowledge of several parameters to a high accuracy, in particular, the emission cross-section spectrum of Er in the host under study . An understanding of the amplifier [1] temperature dependent characteristics is of a great importance. Erbium-doped planar waveguides are being studied because of their applications as integrated optical amplifiers or lasers that operate at 1.5 ì m. The rare earth ion Er has one of its intra-4f transitions 3+ around 1.53 ì m, coinciding with the low-loss window of standard silica optical fibers. Optical amplifiers at this wavelength are necessary to overcome losses in the processing and distribution of optical signals, while maintaining high bandwidth and low cross talk. The use of planar amplifiers offers the important advantage that they can be integrated together with other waveguide devices on a single chip . [2] The performance of an Er-doped amplifier depends on the magnitude and wavelength dependence of the emission and absorption cross sections. Together with the Er concentration profile, the optical intensity profile and the waveguide loss, the knowledge of these parameters enables a first-order estimate of the 2 3 potential optical gain. Al O waveguide films on silicon wafers are interesting as a host material for Er because waveguide fabrication technology is well developed for this material . [3] One can theoretically analyze the temperature dependent of both emission cross section and gain. The approximate McCumber procedure is often used to predict the emission cross-section spectrum of the 1.5- ì m transition of Er-doped glass fibers from the transition's measured absorption spectrum at different values of temperature . The objective of this paper [4] is to calculate the emission cross section of the Er- 2 3 doped Al O waveguide from the absorption cross section at different temperature values using McCumber procedure, and then calculate the expected values of gain coefficient at different population inversion factors for different temperature values. Also, the gain of the amplifier at different input power at different temperature values is studied. II-Theory 1. Calculation of the Emission Cross Section: The McCumber relation states that the absorption cross a e section, ó ( í ), and the emission cross section, ó ( í ), spectra between a ground state (a manifold of eight 1j sublevels of energy E ) and the excited state (a 2j manifold of seven sublevels of energy E ) are related by [5] (1) where k is the Boltzmann constant, T the absolute temperature and í the optical frequency. The parameter å is defined as (2) o 21 11 where E = E – E is the energy difference between the lowest energy levels of the two manifolds. Relation (1) can be written in the form [5] (3)