Zakery / Elliott Optical Nonlinearities in Chalcogenide Glasses and their Applications

1. Auflage 2007
ISBN: 978-3-540-71068-4
Verlag: Springer
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 135, 211 Seiten, eBook

Reihe: Springer Series in Optical Sciences

Photonics,whichusesphotonsforinformationandimageprocessing,islabeled as one of the technologies of the 21st century, for which nonlinear op- cal processes provide the key functions of frequency conversion and optical switching. Chalcogenide glasses are based on the chalcogen elements S, Se, and Te. These glasses are formed by the addition of other elements such as Ge, As, Sb, Ga, etc. These glasses are low-phonon energy materials and are generally transparentfromthevisibletoinfrared.Chalcogenideglassescanbedopedby rare-earth elements such as Er, Nd, Pr, etc., and hence numerous applications ofactiveopticaldeviceshavebeenproposed.Theseglassesareopticallyhighly nonlinear and could therefore be useful for all-optical switching. This book is a review of recent progress in the science and technology of chalcogenide glasses, with an emphasis on their nonlinear optical properties, forgraduatestudents,practisingengineersandscientistsfromawidemultid- ciplinary area such as physics, chemistry, electrical engineering and material science. Since the interest in this area is growing worldwide, a book dealing with this subject will be of great value to researchers of varied backgrounds. Chalcogenide glasses and their electronic, structural, and photoinduced properties are introduced. Techniques to characterize the linear and nonlinear optical properties of these glasses are introduced and used to measure the optical constants of chalcogenide glasses in the form of bulk, thin ?lm and ?ber. The possibilities of fabricating passive and active devices are presented.

Zielgruppe

Research

Autoren/Hrsg.

Zakery, A.

Elliott, S.R.

Inhaltsverzeichnis

An Introduction to Chalcogenide Glasses.- Basic Concepts of Nonlinear Optics.- Experimental Techniques to Measure Nonlinear Optical Constants.- Measurement of Nonlinear Optical Constants.- Optical Nonlinearities in Chalcogenide Fibres.- Optical Switching in Chalcogenide Glasses.- Issues and Future Directions.

Leseproben

1 An Introduction to Chalcogenide Glasses (p. 1-2)

1.1 Introduction

Chalcogenide glasses are based on the chalcogen elements S, Se, and Te. These glasses are formed by the addition of other elements such as Ge, As, Sb, Ga, etc. They are low-phonon-energy materials and are generally transparent from the visible up to the infrared. Chalcogenide glasses can be doped by rareearth elements, such as Er, Nd, Pr, etc., and hence numerous applications of active optical devices have been proposed. Since chalcogenide-glass .bers transmit in the IR, there are numerous potential applications in the civil, medical, and military areas. Passive applications utilize chalcogenide .bers as a light conduit from one location to another point without changing the optical properties, other than those due to scattering, absorption, and re.ection. These glasses are optically highly nonlinear and could therefore be useful for all-optical switching (AOS). Chalcogenide glasses are sensitive to the absorption of electromagnetic radiation and show a variety of photoinduced e.ects as a result of illumination. Various models have been put forward to explain these effects, which can be used to fabricate diffractive, waveguide and fiber structures. For recent reviews, see [1–4]. Next-generation devices for telecommunication and related applications will rely on the development of materials which possess optimized physical properties that are compatible with packaging requirements for systems in planar or fiber form. This allows suitable integration to existing fiber-based applications, and hence requires appropriate consideration as to material choice, stability, and long-term aging behavior.

1.2 Structure of Chalcogenide Glasses

Solids are a particular state of condensed matter characterized by strong interactions between the constituent particles (atoms, molecules). Solids can be found or prepared either in an ordered (crystalline) state or in a disordered (noncrystalline) state. While the ordered state of a solid is limited to only de.ned. An ideal crystal corresponds to a regular arrangement of atoms in a lattice with well-de.ned symmetry, and a structural unit called the unit cell can be de.ned. Translation of the unit cell along the three coordinate axes reproduces the whole assembly of atoms. A real crystal does not exhibit perfect periodicity in space and contains various kinds of imperfections or defects. Solids which lack the periodicity of the atoms are called noncrystalline solids or amorphous, vitreous or glassy solids. While crystals possess long-range order (LRO), in amorphous materials short-range order (SRO) still exists.

Although the first and second nearest-neighbor coordination shells are wellde fined, atoms in the third coordination sphere start to become uncorrelated with those in the first one. In other words, the limit of short- and mediumrange order is the first 3–4 interatomic distances. The price to be paid for the loss of LRO is the appearance of .uctuations in angles and distances between the bonds. The ideal noncrystalline network is di.cult to define. Particularly, different thermal treatments lead to various noncrystalline arrangements of atoms. A continuous random network [5] might be considered to be an ideal noncrystalline network for covalent solids.