Preface xv About the Companion Website xvii 1 Light and Colour 1 1.1 Light and Colour 1 1.1.1 Light rays 1 1.1.2 Light waves 2 1.1.3 Photons 3 1.

1.4 Energy levels 4 1.1.5 Waves and particles 5 1.1.6 Colour 6 1.2 Light Waves 6 1.3 Light Waves and Colour 8 1.

4 Interference 9 1.4.1 Two waves with the same wavelength 9 1.4.2 Two waves with different wavelengths 10 1.4.3 Phase and group velocity 11 1.4.

4 Light pulses 12 1.4.5 Superluminal and subluminal light 14 1.5 Light Sources 15 1.6 Incandescence 16 1.6.1 Incandescence and black-body radiation 16 1.6.

2 The colour of incandescent objects 17 1.7 Luminescence 18 1.8 Laser Light 20 1.8.1 Emission and absorption of radiation 20 1.8.2 Energy-level populations 22 1.8.

3 Rates of absorption and emission 23 1.8.4 Cavity modes 25 1.8.5 Coherence length and bandwidth 26 1.8.6 Supercontinuum light 27 1.9 Vision 28 1.

10 Colour Perception 33 1.11 Additive Coloration 34 1.12 Subtractive Coloration 37 1.13 The Interaction of Light with a Material: Appearance 39 1.13.1 Reflection 39 1.13.2 Diffuse reflectance 40 1.

13.3 Elastic scattering 41 1.13.4 Inelastic scattering 42 1.13.5 Absorption 42 1.13.6 Attenuation 43 1.

13.7 Structural colour, iridescence, and electron excitation colour 45 Further Reading 46 Problems and Exercises 48 2 Colour Due to Refraction and Dispersion 51 2.1 Refraction and the Refractive Index of a Material 51 2.2 Total Internal Reflection 55 2.2.1 Refraction at an interface 55 2.2.2 Evanescent waves 56 2.

3 Refractive Index and Polarisability 58 2.4 Refractive Index and Density 61 2.5 Invisible Animals, GRINS, and Mirages 63 2.6 Dispersion and Colours Produced by Dispersion 65 2.7 Rainbows 68 2.8 Halos 74 2.9 Fibre Optics 74 2.9.

1 Optical communications 74 2.9.2 Optical fibres 75 2.9.3 Attenuation in glass fibres 77 2.9.4 Chemical impurities 78 2.9.

5 Dispersion and optical fibre design 80 2.10 Metamaterials and Negative Refractive Index 83 2.10.1 Metamaterials 83 2.10.2 Hyperlenses 84 2.10.3 Invisibility cloaks 87 2.

10.4 Metasurfaces and flat lenses 88 2.11 The Electro-Optic Effect and Photorefractive Materials 88 Further Reading 90 Problems and Exercises 92 3 The Production of Colour by Reflection 95 3.1 Reflection from a Single Surface 96 3.1.1 Reflection from a transparent plate 96 3.1.2 Data storage using reflection 97 3.

2 Reflection from a Single Thin Film in Air 98 3.2.1 Reflection perpendicular to the film 98 3.2.2 Variation with viewing angle 101 3.2.3 Transmitted beams 102 3.3 The Colour of a Single Thin Film in Air 103 3.

4 The Reflectivity of a Single Thin Film in Air 105 3.5 The Colour of a Single Thin Film on a Substrate 106 3.6 The Reflectivity of a Single Thin Film on a Substrate 107 3.7 Low-Reflection and High-Reflection Films 108 3.7.1 Antireflection coatings 108 3.7.2 Antireflection layers 109 3.

7.3 Graded index antireflection coatings 111 3.7.4 High reflectivity surfaces 113 3.7.5 Interference modulated (IMOD) displays 113 3.8 Multiple Thin Films 114 3.8.

1 Dielectric mirrors 114 3.8.2 Multilayer stacks 116 3.8.3 Interference filters and distributed Bragg reflectors 117 3.9 Fibre Bragg Gratings 118 3.10 ''Smart'' Windows 120 3.10.

1 Low-emissivity windows 121 3.10.2 Self-cleaning windows 122 3.11 Thin-Film Colours in Nature 123 3.11.1 Single thin-film reflection 123 3.11.2 Multilayer mirrors 124 3.

11.3 Multilayer colour generation 125 3.11.4 Multilayer reflectors in blue butterflies 127 Further Reading 128 Problems and Exercises 129 4 Polarised Light and Crystals 135 4.1 Polarisation of Light 135 4.2 Polarised Light and Vision 137 4.3 Polarisation by Reflection 138 4.4 Polars 141 4.

5 Crystal Symmetry and Refractive Index 143 4.6 Double Refraction: Calcite as an Example 144 4.6.1 Double refraction 144 4.6.2 Refractive index and crystal structure 147 4.7 The Description of Double Refraction Effects 148 4.7.

1 Uniaxial crystals 148 4.7.2 Biaxial crystals 150 4.8 Colour Produced by Polarisation and Birefringence 152 4.9 Dichroism, Trichroism, and Pleochroism 154 4.10 Nonlinear Effects 156 4.10.1 Nonlinear crystals 156 4.

10.2 Second and third harmonic generation 158 4.10.3 Frequency mixing 160 4.10.4 Optical parametric amplifiers and oscillators 161 4.11 Frequency Matching and Phase Matching 162 4.12 More on Second Harmonic Generation 164 4.

12.1 Polycrystalline solids and powders 164 4.12.2 Second harmonic generation in glass 165 4.12.3 Second harmonic and sum frequency generation by organic materials 166 4.12.4 Second harmonic generation at interfaces 166 4.

12.5 Second harmonic microscopy 168 4.13 Optical Activity 168 4.13.1 The rotation of polarised light by molecules 168 4.13.2 The rotation of polarised light by crystals 170 4.13.

3 Circular birefringence and dichroism 171 4.14 Liquid Crystals 172 4.14.1 Liquid crystal mesophases 172 4.14.2 Liquid crystal displays 174 Further Reading 177 Problems and Exercises 179 5 Colour Due to Scattering 183 5.1 Scattering and Extinction 183 5.2 Tyndall Blue and Rayleigh Scattering 186 5.

3 Blue Skies, Red Sunsets 187 5.4 Scattering and Polarisation 190 5.5 Mie Scattering 192 5.6 Blue Eyes, Blue Feathers, and Blue Moons 195 5.7 Paints, Sunscreens, and Related Matters 197 5.8 Multiple Scattering 199 5.9 Gold Sols and Ruby Glass 199 5.10 The Lycurgus Cup and Other Stained Glass 201 Further Reading 204 Problems and Exercises 205 6 Colour Due to Diffraction 209 6.

1 Diffraction and Scattering 209 6.2 Diffraction and Colour Production by a Slit 210 6.3 Diffraction and Colour Production by a Rectangular Aperture 212 6.4 Diffraction and Colour Production by a Circular Aperture 213 6.5 The Diffraction Limit of Optical Instruments 215 6.6 Colour Production by Linear Diffraction Gratings 216 6.7 Two-Dimensional Gratings 221 6.8 Estimation of the Wavelength of Light by Diffraction 223 6.

9 Diffraction by Crystals and Crystal-Like Structures 224 6.9.1 Bragg''s law 224 6.9.2 Opals 226 6.10 Photonic Crystals 229 6.10.1 Artificial and inverse opal structures 229 6.

10.2 Diffraction from cubic photonic crystals 232 6.10.3 The effective refractive index of cubic photonic crystals 232 6.10.4 Dynamical form of Bragg''s law 234 6.10.5 Photonic bandgaps 235 6.

10.6 Photonic crystals in nature 236 6.10.7 Photonic crystal fibres 238 6.11 Diffraction from Disordered Gratings 239 6.11.1 Random specks and droplets 239 6.11.

2 Halos, coronae, and glories 240 6.11.3 Colour from cholesteric liquid crystals 242 6.11.4 Natural helicoidal structures 246 6.11.5 Disordered two- and three-dimensional gratings 247 6.12 Diffraction by Sub-Wavelength Structures 248 6.

12.1 Diffraction by moth-eye antireflection structures 249 6.12.2 The cornea of the eye 250 6.12.3 Some blue feathers 251 6.13 Holograms 252 6.13.

1 Holograms and interference patterns 252 6.13.2 Transmission holograms 253 6.13.3 Reflection holograms 255 6.13.4 Rainbow holograms 256 6.13.

5 Hologram recording media 259 6.13.6 Embossed holograms 261 6.14 Hologram Formation 262 6.14.1 Interference of two coherent light waves 262 6.14.2 Image formation 263 Further Reading 266 Problems and Exercises 268 7 Colour from Atoms and Ions 273 7.

1 The Spectra of Atoms and Ions 273 7.2 The Spectrum of Hydrogen 276 7.3 Terms and Levels 278 7.4 Atomic Spectra and Chemical Analysis 280 7.5 Fraunhofer Lines and Stellar Spectra 282 7.6 Neon Signs and Plasma Displays 283 7.7 The Helium-Neon Laser 285 7.8 Sodium and Mercury Street Lights 287 7.

9 Atomic and Optical Clocks 289 7.9.1 Clocks 289 7.9.2 Atomic clocks 290 7.9.3 The 133Cs atomic clock 291 7.9.

4 Optical clocks 291 7.10 Transition-Metal Cation Colours: Overview 291 7.11 Crystal Field Splitting 292 7.11.1 d-orbital interactions 292 7.11.2 Term splitting 295 7.11.

3 Energies 297 7.11.4 Selection rules 297 7.12 The Crystal Field Colours of Transition-Metal Ions 299 7.12.1 3d1, 3d4, 3d5, 3d6, and 3d9 cations 299 7.12.2 3d2, 3d3, 3d7, and 3d8 cations 301 7.

12.3 Octahedral and tetrahedral coordination 304 7.12.4 Thermochromism, piezochromism, and crystal-field splitting 306 7.13 Crystal Field Colours in Minerals and Gemstones 306 7.13.1 The colour of ruby 306 7.13.

2 Emerald, chrome alum, and alexandrite 309 7.13.3 Malachite, azurite, and turquoise 311 7.14 Colour as a Structural Probe 311 7.15 Transition-Metal-Ion Lasers 313 7.15.1 The ruby laser: a three-level laser 313 7.15.

2 The titanium-sapphire laser 314 7.16 Colours fro.