UUnniivveerrssiittyy ooff CCeennttrraall FFlloorriiddaa SSTTAARRSS Electronic Theses and Dissertations, 2004-2019 2005 HHiigghh GGaaiinn // BBrrooaaddbbaanndd OOxxiiddee GGllaasssseess FFoorr NNeexxtt GGeenneerraattiioonn RRaammaann AAmmpplliififieerrss Clara Rivero University of Central Florida Part of the Electromagnetics and Photonics Commons, and the Optics Commons Find similar works at: https://stars.library.ucf.edu/etd University of Central Florida Libraries http://library.ucf.edu This Doctoral Dissertation (Open Access) is brought to you for free and open access by STARS. It has been accepted for inclusion in Electronic Theses and Dissertations, 2004-2019 by an authorized administrator of STARS. For more information, please contact [email protected]. SSTTAARRSS CCiittaattiioonn Rivero, Clara, "High Gain / Broadband Oxide Glasses For Next Generation Raman Amplifiers" (2005). Electronic Theses and Dissertations, 2004-2019. 611. https://stars.library.ucf.edu/etd/611 HIGH GAIN / BROADBAND OXIDE GLASSES FOR NEXT GENERATION RAMAN AMPLIFIERS by CLARA A. RIVERO B.S. University of Central Florida, 2001 M.S. University of Central Florida, 2003 A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Optics in the College of Optics and Photonics at the University of Central Florida Orlando, Florida Fall Term 2005 Major Professors: Kathleen C. Richardson and George I. Stegeman © 2005 Clara A. Rivero ii INTER-UNIVERSITY AGREEMENT ON JOINT DOCTORATE SUPERVISION between BORDEAUX 1 UNIVERSITY AND UNIVERSITY OF CENTRAL FLORIDA University of Bordeaux 1 recognizes the validity of the thesis and therefore awards le grade de docteur de l’Université Bordeaux 1 par Clara A. RIVERO Spécialité : Physico-chimie de la Matière Condensée This thesis is under the joint supervision of : - at Bordeaux 1 University by: Dr. Thierry CARDINAL Chargé de Recherche (Sciences Chimiques) And Dr. Evelyne FARGIN Professor (Sciences Chimiques) - and at University of Central Florida by: Dr. Kathleen RICHARDSON Director and Professor (Materials Science and Engineering) And Dr. George STEGEMAN Professor (Optics, Physics and ECE) iii RESUME L’intérêt pour l’amplification optique par effet Raman suscite un vif regain d’intérêt en raison de la nécessité d’accroître rapidement la bande passante dans le domaine des télécommunications, tant pour les liaisons longues distances que pour les réseaux locaux. Cet engouement s’appuie sur les récents développements de l’industrie du transport de l’information par fibre optique et sur l’évolution de la technologie des diodes laser. Par rapport aux amplificateurs par fibres dopés par des ions terres rares, pour lesquels la gamme spectrale est fixe et limitée, la bande spectrale de gain Raman est plus large et les longueurs d’onde accessibles sont déterminées uniquement par la longueur d’onde d’excitation et la largeur spectrale du milieu Raman actif. Dans ce contexte, les verres inorganiques représentent des matériaux de choix de part leur réponse spectrale relativement large et la possibilité d’obtention aisée de fibres optiques. Le travail de thèse décrit les résultats obtenus sur différents verres oxydes qui ont été synthétisés et caractérisés en vue d’une utilisation comme milieu à gain Raman. Des mesures de diffusion Raman spontanée, de gain Raman, d’indice de réfraction et d’absorption par une technique de déflection thermique ont été menées sur ces échantillons vitreux afin d’établir des corrélations entre les réponses optiques, la composition chimique des matériaux et la structure du réseau vitreux. Deux familles de matériaux vitreux ont été explorées: des matrices vitreuses phosphates pour l’obtention de larges spectres de gain Raman et des matrices tellurites pour atteindre de forts coefficients d’amplification Raman. Les verres de type phosphate ont été choisis afin d’atteindre une amplification Raman jusqu’à 1000 cm-1, tandis que les verres tellurites ont été sélectionnés pour leur fort gain Raman relié à la forte polarisabilité et hyperpolarisabilité de ces iv matériaux. Les résultats obtenus lors de la thèse montrent que les matrices phosphates donnent effectivement accès à des largeurs de bande spectrale de gain Raman jusqu’à 40 THz, ce qui représente une augmentation d’un facteur 5 par rapport à SiO . Les verres tellurites, quant à eux, 2 s’avèrent bien être de bons candidats pour des applications à fort gain Raman discret en atteignant des coefficients de gain Raman s’élevant à 50 fois ceux obtenus avec SiO à 1064 nm. 2 Bien que les mesures de diffusion Raman spontanée constituent une méthode courante pour estimer l’amplitude et la gamme spectrale de gain Raman dans les matériaux, en particulier pour les verres inorganiques, une analyse précise des résultats nécessite de prendre en compte l’influence de la proximité de la longueur d’onde d’excitation avec la longueur d’onde de coupure du matériau à la frontière de l’UV et du visible. Une dépendance en fonction de la longueur d’onde a été mise en évidence ainsi qu’un phénomène de résonance lorsque la mesure est conduite près du front d’absorption. Cet effet, développé dans le manuscrit, est attribué au couplage entre les transitions électroniques et les modes vibrationnels. v ABSTRACT Interest in Raman amplification has undergone a revival due to the rapidly increasing bandwidth requirements for communications transmission, both for long haul and local area networks, and recent developments in the telecom fiber industry and diode laser technology. In contrast to rare earth doped fiber amplifiers, for which the range of wavelengths is fixed and limited, Raman gain bandwidths are larger and the operating wavelength is fixed only by the pump wavelength and the bandwidth of the Raman active medium. In this context, glasses are the material of choice for this application due to their relatively broad spectral response, and ability of making them into optical fiber. This dissertation summarizes findings on different oxide-based glasses that have been synthesized and characterized for their potential application as Raman gain media. Different techniques were deployed for characterization purposes, which include primarily spontaneous Raman scattering measurements, direct nonlinear Raman gain measurements, linear refractive index measurements, and a photothermal deflection technique for measurement of the absorption coefficient of these samples, among others. Two main glass families were investigated: phosphate-based glass matrices for broadband Raman gain application and TeO -based glasses for high Raman gain amplification. 2 A phosphate network was preferred for the broadband application since the phosphate Raman active modes can provide amplification above 1000 cm-1, whilst TeO -based glasses were 2 selected for the high gain application due to their enhanced nonlinearities and polarizabilities among the other oxide-based network formers. The results summarized in this dissertation show that phosphate-based glasses can provide Raman amplification bandwidths of up to 40 THz, an vi improvement of almost 5 times the bandwidth of SiO . On the other hand, tellurite-based glasses 2 appear to be promising candidates for high gain discrete Raman applications, providing peak Raman gain coefficients of up to 50 times higher than SiO , at 1064 nm. 2 Although, visible spontaneous Raman scattering cross-section measurement is the most frequently used tool for estimating the strength and spectral distribution of Raman gain in materials, especially glasses, there are some issues that one needs to be aware when conducting these measurements near the absorption band edge of the material. This led to the detection of an inherent frequency-dispersion in the Raman susceptibility and a resonant enhancement phenomenon when measurements were conducted near the absorption edge of the material. This effect is caused by a coupling between the electronic and vibrational modes, as it will be discussed in details in this dissertation. vii To my family for their never ending love and support, specially my grandparents and my parents… To Cesar, Mariclaudia, and Juliet, may this serve you as an inspiration to find the path of your own life… To Erwan, for changing my life. viii ACKNOWLEDGMENTS I have been extraordinarily blessed throughout my life, and in particular during the last four years. In the summer of 2001, after having completed my B.S. in Physics, I sat with Dr. Kathleen Richardson in her office. After a long conversation about my future aspirations and perspective, she asked if I wanted to pursue a PhD under her advisement. This was the beginning of an amazing experience that will influence the rest of my life. For believing in me, the knowledge and opportunity she shared with me, her unconditional support, the “doors” she opened, the dreams she made come true; I will always remain grateful. She is my role model and endeared friend. I have been privileged to have Dr. George Stegeman as a second advisor. He assisted me in fellowship opportunities, adopted me into his group, and has graciously served as my “official” dissertation committee chair. It has been an honor to work with him and learning from him. With great admiration and respect for him as a scientist and a person I will call him “George”. I am deeply appreciative that he considered me part of his group with all the responsibilities, and for the continuous support he offered me throughout my PhD. If I am to reflect on my fortune as two fold for the support of Kathleen Richardson and George Stegeman, then I must extend it to four fold. I was also privileged of having two “French” advisors, Dr. Thierry Cardinal and Dr. Evelyne Fargin. This dissertation is part of a co- tutelle agreement between the University of Central Florida and the University of Bordeaux I. At the end of my study I will receive two doctorate diplomas, one in the field of Optics from CREOL and another in Materials Science from ICMCB. I have been blessed beyond measure. I ix