Optical nonlinearities in chalcogenide glasses and their applications

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.

1 An Introduction to Chalcogenide Glasses	p. 1
1.1 Introduction	p. 1
1.2 Structure of Chalcogenide Glasses	p. 1
1.3 Electronic Properties of Chalcogenide Glasses	p. 6
1.3.1 Electronic States in Chalcogenide Glasses	p. 6
1.3.2 Measurements of the Absorption Coefficient and the Optical Gap	p. 8
1.4 Chalcogenide Glasses for Near-Infrared Optics	p. 10
1.5 Chalcogenide Glasses for Mid-IR and Far-IR Applications	p. 12
1.6 Bulk Chalcogenide Glasses, Composition, and Optical Constants	p. 14
1.7 Chalcogenide Thin Films and Comparison with the Bulk	p. 17
1.8 Photoinduced Changes in Chalcogenide Glasses	p. 21
1.8.1 Photoinduced Phenomena	p. 21
1.8.2 Exposure Characteristics	p. 23
1.8.3 Measurements of the Propagation Losses by a Prism Coupler	p. 25
1.8.4 Measurements of Propagation Losses in Laser-Written Waveguides	p. 26
1.9 Summary	p. 27
2 Basic Concepts of Nonlinear Optics	p. 29
2.1 Polarization	p. 29
2.2 Wave Equation	p. 30
2.2.1 Linear Optics	p. 31
2.2.2 Nonlinear Optics	p. 34
2.3 The Harmonic Oscillator Model in Linear Optics	p. 37
2.4 The Anharmonic Oscillator Model in Nonlinear Optics	p. 40
2.5 Properties of Anisotropic Media	p. 42
2.6 Second-Harmonic Generation	p. 43
2.7 Self-Phase Modulation and Soliton Generation	p. 44
2.7.1 Optical Solitons	p. 45
2.7.2 Mechanisms of Nonlinearity	p. 47
2.7.3 Optical Phase Conjugation	p. 48
2.7.4 Optical Bistability	p. 50
2.7.5 Stimulated Raman Scattering	p. 51
2.7.6 Third-Harmonic Generation	p. 52
3 Experimental Techniques to Measure Nonlinear Optical Constants	p. 55
3.1 Introduction	p. 55
3.2 Degenerate Four-Wave Mixing	p. 55
3.3 Nearly Degenerate Three-wave Mixing	p. 59
3.4 Z-Scan	p. 61
3.5 Third-Harmonic Generation	p. 63
3.6 Optical Kerr Gate and Ellipse Rotation	p. 64
3.6.1 Optical Kerr Gate	p. 64
3.6.2 Ellipse Rotation	p. 66
3.7 Self-Phase Modulation	p. 67
3.8 Spectrally Resolved Two-Beam Coupling	p. 69
3.9 Mach-Zehnder Interferometry	p. 70
3.10 Summary	p. 73
4 Measurement of Nonlinear Optical Constants	p. 75
4.1 Measurements of Nonlinear Refractive Index n 2	p. 75
4.2 Measurements of Nonlinear Absorption Coefficient ß	p. 91
4.3 Determination of Three Photon-Absorption and Multiphoton Absorption	p. 94
4.4 Second-Harmonic Generation, Phase Conjugation, etc	p. 95
4.5 Comparison of Chalcogenide Nonlinearities with Silica	p. 102
5 Optical Nonlinearities in Chalcogenide Fibres	p. 107
5.1 Fabrication of Chalcogenide Fibers and Their Linear Optical Properties	p. 107
5.1.1 Fabrication of Fibers by Extrusion	p. 108
5.1.2 Physical and Linear Optical Properties of Chalcogenide Fibers	p. 109
5.2 Nonlinear Optical Properties of Fibers	p. 111
5.2.1 Features of Chalcogenide Glass as a Nonlinear Material	p. 111
5.2.2 Stimulated Light Scattering and Super-Continuum Generation	p. 112
5.2.3 Second-Order Nonlinearity in Poled Glass	p. 113
5.3 Pulse Propagation in Fibers	p. 114
5.3.1 Propagation of Optical Fields	p. 114
5.3.2 Nonlinear Pulse Propagation	p. 116
5.3.3 Higher-Order Nonlinear Effects	p. 120
5.4 Group-Velocity Dispersion Compensation by Fiber Gratings	p. 121
5.5 Applications	p. 122
6 Optical Switching in Chalcogenide Glasses	p. 129
6.1 Criteria of Material Properties for All-optical Switching	p. 129
6.2 Design Issues for All-Optical Switching	p. 131
6.3 All-Optical Switching in Chalcogenide Glasses	p. 131
6.3.1 All-Optical Switching using Chalcogenide Glass Fibers	p. 131
6.3.2 All-Optical Switching in Thin Chalcogenide Films	p. 137
6.4 All-Optical Switches, AND Gate, NOR Gate, etc	p. 145
6.4.1 Introduction	p. 145
6.4.2 Nonlinear Interferometric Devices	p. 147
6.4.3 Nonlinear Beam-Coupling Devices	p. 147
6.4.4 Polarization Switching Devices	p. 148
6.4.5 Soliton Switching Devices	p. 148
6.5 Limitations of All-Optical Switches	p. 149
6.6 Summary	p. 149
7 Issues and Future Directions	p. 151
7.1 Optical Limiting	p. 151
7.2 Second-Harmonic Generation and Electro-Optic Effects	p. 153
7.3 Fabrication of Rib and Ridge Waveguides and of Fiber Gratings	p. 155
7.4 All-Optical Nonlinear Integrated Circuits	p. 166
7.5 Inclusion of Metal Nanoparticles to Enhance Nonlinearity	p. 168
7.6 Other Applications	p. 169
7.7 Summary	p. 175
References	p. 177
Index	p. 195

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