www.wiley.com/go/meoa

Series Editors

Professor Arthur Willoughby, University of Southampton, Southampton, UK

Dr Peter Capper, formerly of SELEX Galileo Infrared Ltd, Southampton, UK

Professor Safa Kasap, University of Saskatchewan, Saskatoon, Canada

Published Titles

Bulk Crystal Growth of Electronic, Optical and Optoelectronic Materials, Edited by P. Capper

Properties of Group-IV, III–V and II–VI Semiconductors, S. Adachi

Charge Transport in Disordered Solids with Applications in Electronics, Edited by S. Baranovski

Optical Properties of Condensed Matter and Applications, Edited by J. Singh

Thin Film Solar Cells: Fabrication, Characterization, and Applications, Edited by J. Poortmans and V. Arkhipov

Dielectric Films for Advanced Microelectronics, Edited by M. R. Baklanov, M. Green, and K. Maex

Liquid Phase Epitaxy of Electronic, Optical and Optoelectronic Materials, Edited by P. Capper and M. Mauk

Molecular Electronics: From Principles to Practice, M. Petty

CVD Diamond for Electronic Devices and Sensors, Edited by R. S. Sussmann

Properties of Semiconductor Alloys: Group-IV, III–V, and II–VI Semiconductors, S. Adachi

Mercury Cadmium Telluride, Edited by P. Capper and J. Garland

Zinc Oxide Materials for Electronic and Optoelectronic Device Applications, Edited by C. Litton, D. C. Reynolds, and T. C. Collins

Lead-Free Solders: Materials Reliability for Electronics, Edited by K. N. Subramanian

Silicon Photonics: Fundamentals and Devices, M. Jamal Deen and P. K. Basu

Nanostructured and Subwavelength Waveguides: Fundamentals and Applications, M. Skorobogatiy

Photovoltaic Materials: From Crystalline Silicon to Third-Generation Approaches, G. Conibeer and A. Willoughby

Glancing Angle Deposition of Thin Films: Engineering the Nanoscale, Matthew M. Hawkeye, Michael T. Taschuk, and Michael J. Brett

Spintronics for Next Generation Innovative Devices, Edited by Katsuaki Sato and Eiji Saitoh

Physical Properties of High-Temperature Superconductors, Rainer Wesche

Wiley Series in Materials for Electronic and Optoelectronic Applications

This book series is devoted to the rapidly developing class of materials used for electronic and optoelectronic applications. It is designed to provide much-needed information on the fundamental scientific principles of these materials, together with how these are employed in technological applications. The books are aimed at (postgraduate) students, researchers, and technologists, engaged in research, development, and the study of materials in electronics and photonics, and industrial scientists developing new materials, devices, and circuits for the electronic, optoelectronic, and communications industries.

The development of new electronic and optoelectronic materials depends not only on materials engineering at a practical level, but also on a clear understanding of the properties of materials, and the fundamental science behind these properties. It is the properties of a material that eventually determine its usefulness in an application. The series therefore also includes such titles as electrical conduction in solids, optical properties, thermal properties, and so on, all with applications and examples of materials in electronics and optoelectronics.

The characterization of materials is also covered within the series in as much as it is impossible to develop new materials without the proper characterization of their structure and properties. Structure–property relationships have always been fundamentally and intrinsically important to materials science and engineering.

Materials science is well known for being one of the most interdisciplinary sciences. It is the interdisciplinary aspect of materials science that has led to many exciting discoveries, new materials, and new applications. It is not unusual to find scientists with a chemical engineering background working on materials projects with applications in electronics. In selecting titles for the series, we have tried to maintain the interdisciplinary aspect of the field, and hence its excitement to researchers in this field.

Arthur Willoughby
Peter Capper
Safa Kasap

The pleasure of scientific and philosophical expression or communication prompts deeper thinking, which, as human beings, we share for promoting knowledge. Sharing and dissemination of knowledge is the second greatest charity, after saving and protecting life and the environment – that is what my parents taught me! Without this beacon of knowledge in human beings, civilization will remain trapped in the labyrinth of darkness. Can we imagine human civilization without any epic of knowledge – where we would be today as a civilization? These are very powerful statements and as an academic I sincerely believe in the true pursuit of knowledge and, for me, this pursuance became a reality when I completed this book.

Several years ago some of my distinguished colleagues asked me whether I would be willing to write a book on “Inorganic Glasses for Photonics”, to fill a gap in this important area of physical and materials science. Perhaps it is appropriate to state at this point the importance of the subject area without emphasizing it too much. No engineering discipline can grow without materials science and vice versa. We chose the title Inorganic Glasses for Photonics because it bears two key aspects of materials science, the structure of the glassy state and its suitability for functionalizing properties for photonic applications. The study of structure–property relationships is an intrinsic part of understanding materials science, and in this book I have attempted to bring out this feature in every chapter in a concise and contextual manner, and wherever possible with examples.

During the course of writing this book, as expected, I faced many challenges and, in most cases, I turned these challenges into opportunities for learning new experiences, which helped me in forming my thoughts to adopt a different style of expression. This may become apparent to those who seek to understand the structure–property relationship of materials. Before writing a complex section, I often felt that my thoughts were in a whirlwind of thermal and configurational entropy, and that the energy requirement for achieving a coherence of thoughts, as in the manner of a laser cavity, was too high. Consequently the “slope efficiency” for writing each chapter was not the same. Exemplifying the structure–property relationship was not easy, which becomes apparent in some sections of the book, and I am sure this feature will continue to evolve in future. For this, if the readers feel there are omissions I apologize in advance. However, I have purposely kept away from incorporating chapters and sections that are well covered in other established text books in the related subject areas.

Not realizing at the outset of writing this textbook that the year 2015 would be declared by the United Nations as the Year of Light, in which year I would be able to finish this textbook, the conclusion of this project brought a personal sense of achievement. One hundred years ago in 1915, Albert Einstein rose to world fame by explaining new properties of light in the context of general relativity. Einstein also discovered two other important aspects of light and matter – the discovery of Brownian motion helped in confirming the value of Avogadro's number independently. Einstein's Nobel Prize winning work on the photoelectric effect is at the genesis of quantum theory. A chance to celebrate the great achievements of Einstein in the form of a book on “Inorganic Glasses for Photonics” is an infinitesimal contribution to the world community of scientists and engineers.

In this book there are seven chapters, which in future may grow into much fuller shape by incorporating emerging aspects of nonlinear optics, nano-photonics and plasmonics using inorganic glass as a medium for controlling and manipulating light. Although I have written a significant section on nonlinear optics in Chapter 7, the aspects of nano-photonics and plasmonics are not discussed because I feel these two areas have not yet reached maturity in terms of using glass as a medium for wider device applications. I hope that you would agree!

In Chapter 1, the main focus is on the glass science and structures of inorganic glasses that are commonly used for photonic devices. A range of inorganic glasses are discussed in this chapter, with examples of oxide, fluoride, chalcogenide and mixed anion glasses. I have also attempted to explain the thermodynamics of glass-forming liquids in the vicinity of deep eutectic liquid, which is often the composition range for stable glass formation. The theory of co-ordination number is also discussed in the context of phonon structure.

For photonic device applications, a chosen glass composition must be engineered using the thermal, physical and viscosity properties of a glass. These properties are discussed in Chapter 2 by emphasizing the roles of nucleation and crystal growth, e.g. for fibre drawing.

Having discussed the important thermal, viscosity and physical properties of glasses in Chapter 2, in Chapter 3 the fabrication of bulk inorganic glasses using melting and casting is discussed for a majority of known inorganic glasses. In this chapter the fabrication principles of glass-ceramic materials are also discussed. The theory of sol–gel formation and sol–gel based glass fabrication are also discussed briefly in this chapter.

In Chapter 4, I have introduced the standard geometrical optics for fibre optics and briefly discussed the Maxwell's equation for modal analysis and its importance in fibre and waveguide optics. In this chapter I have also brought together the signal degradation mechanism in waveguides and discussed them in some detail, by making comparisons. In this approach I have also attempted to bring together the properties of various glasses for fibre and waveguide fabrication. This chapter concludes with a detailed discussion on refractive index and its dependence on compositions, density, temperature and stress. The relationship of these properties in controlling bulk optical properties is especially emphasized.

In Chapter 5, the main emphasis is on the methods of thin-film fabrication using physical and chemical vapour deposition and pulsed laser deposition including ion implantation techniques. The pros and cons of each technique are discussed with some examples.

I have adopted a different style of presentation in Chapter 6, starting with an introduction to classical radiative transition theory based on dipole models, and have then explained the concept of dipoles and electron–phonon coupling in the text. By emphasizing various quantum mechanical rules, I have then attempted to discuss the radiative, non-radiative, energy transfer and upconversion processes. In view of a wealth of information on rare-earth doped glass based lasers and amplifiers, my focus has been on exemplifying the significance of a set of optical transitions for specific rare-earth ions in selected glass based devices for explaining the structure–property relationships.

The final chapter 7 is on the photonic device applications of inorganic glasses, fibres and waveguides. In this context I have discussed the importance of dispersion and dispersion control in optical fibres, unconventional fibres, namely, microstructured fibres, optical nonlinearity and finally concluding with examples of three- and four-level lasers and their applications. The book concludes with a short discussion on the emerging opportunities for inorganic glasses.

To help readers, there is an extensive list of references and supplementary references for further reading and in-depth comprehension of topical areas.

Earlier this year, in January 2015, Dr Charles Townes, who discovered masers, passed away 6 months before reaching his 100^th birthday, and in this context the Optical Society of America's OPN monthly journal (May 2015 issue, pp. 44–51) published a feature article on the late Dr Townes. In the inset of this article the “Family Matters” of the Townes–Schawlow were also printed. Here is an excerpt that is quite a profound metaphor, and it goes like this: “Tiny rabbit and beaver were looking up at the Hoover Dam. The beaver is saying to the rabbit, ‘No I didn't build it, but it was based on an idea of mine”. Since the discovery of masers in 1953 and then of lasers in 1960, today we are in the era of ultrafast femto- and atto-second lasers. The beavers have long gone, but the Hoover Dam continues to pour out knowledge. For me, it will be truly sensational to produce the most coherent and the purest form of light. Today, glass-based fibre lasers have been commoditized for manufacturing and materials processing. I hope that this book might help burgeoning minds to discover new sources of light, perhaps using novel glasses that are not yet discovered. Such engineered materials might make a significant impact in future.

Animesh Jha
July 2015, University of Leeds, Leeds (UK)