Solitons in Nonlocal Media

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Abstract Optical communications are fundamental in our society based upon infor- mation, allowing the sharing of large amounts of data all around the world. A great deal of attention has been devoted to all-optical methods for infor- mation processing, as they could improve the available technology. In this context nonlinear optics is a key tool to reach such goal. A lot of attention from the scientific community has been paid to spatial solitons, i.e. shape- preserving nonlinear waves, for their ability to guide signals. In particular, an important role is played by solitons in nonlocal media, because in these materials a soliton can be employed as a waveguide for signals even at longer wavelength, paving the way to the design of reconfigurable communication networks via all-optical methods. Nonlocality also mediates the interaction between spatially separated beams, making new applications feasible. In this thesis I focus on highly nonlocal media, in particular on the nematic liquid crystals (NLC), with a high value and non-resonant behavior of their nonlinearity, allowing solitons formation at a few mW and in a large range of wavelengths. The outline of this thesis is as follows. In the first chapter I briefly introduce spatial solitons and reorientational nonlinearity in NLC. In the second chapter I show experimental and theoretical investigation on single soliton propagation in NLC. In the third chapter I discuss, theoret- ically and numerically, the interplay between nonlocality and nonlinearity in finite-size samples and their effect on beam trajectory, comparing the results with experiments performed in NLC. In chapter 4 I investigate solitons composed by two beams of different wavelengths. Finally, in chapter 5 I discuss light amplification and solitons in dye-doped NLC. The results of this thesis enlighten a large number of new approaches for the optical signal processing which can be implemented in nonlocal media, and in particular the main role played by NLC and solitons in this context.
Page 1: Solitons in Nonlocal Media Alessand
Page 5 and 6: Acknowledgements First, I would lik
Page 7 and 8: CONTENTS 2.5.2.2 Soliton Profile .
Page 9 and 10: CONTENTS D List of Publications 118
Page 11 and 12: LIST OF FIGURES 2.4 Reorientation a
Page 13 and 14: LIST OF FIGURES 3.2 (a,b) Perturbat
Page 15 and 16: LIST OF FIGURES 3.11 (a) Equivalent
Page 17 and 18: LIST OF FIGURES 4.3 Plot of vector
Page 19 and 20: LIST OF FIGURES 5.5 Beam profiles a
Page 21 and 22: 1 Introduction 1.1 Solitons in Nonl
Page 23 and 24: 1.3 Nonlocality (6), according to t
Page 25 and 26: 1.3 Nonlocality specified, from her
Page 27 and 28: 1.3.2 Weak Nonlocality 1.4 Liquid C
Page 29 and 30: 1.4 Liquid Crystals possess cylindr
Page 31 and 32: δ = arctan ǫa sin(2θ) ǫa+2ǫ⊥
Page 33 and 34: 1.5 Spatial Solitons in Nematic Liq
Page 35 and 36: 2 Scalar Solitons in Nematic Liquid
Page 37 and 38: 2.3 Effect of the Input Interface F
Page 39 and 40: ǫ sin 2 ξbulk + ǫ⊥ cos 2 d ξ
Page 41 and 42: (a) Ordinary and extraordinary wave
Page 43 and 44: (a) Soliton trajectories in the pla
Page 45 and 46: 2.5 Theory of Nonlinear Optical Pro
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2.5 Theory of Nonlinear Optical Pro
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2.5 Theory of Nonlinear Optical Pro
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3.1 Definition form ρ = ρ(I = 0)+
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3.2 Role of the Boundary Conditions
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3.3 Soliton Trajectory In the rest
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3.3 Soliton Trajectory to n = 1 is
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3.4 Soliton Oscillations in a Finit
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4.2 Cell Geometry and Basic Equatio
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powers, I can linearize δǫtt and,
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eing Ψ0 = Ψ (1) 0 + Ψ(2) 0 matio
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4.3 Highly Nonlocal Limit Writing e
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4.3 Highly Nonlocal Limit If beam 1
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4.4 Breathing 4.4.1 Coupling Geomet
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4.4 Breathing Figure 4.6: Color-cod
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4.4 Breathing distribution. The sim
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5.2 Light Self-Confinement in Dye D
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5.3 Constant Optical Amplification
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5.4 Role of Gain Saturation Figure
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G(s=1.5mm) 1.4 1.3 1.2 1.1 1 (a) 40
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5.4.2 Gain Saturation: Numerical An
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5.6 Co-Propagating Pump such that t
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6 Conclusions In this thesis I have
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A.1 Scattering in a NLC Cell displa
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A.2 Derivation of the Electromagnet
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A.2 Derivation of the Electromagnet
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B.1.1 Optical Equation B.1 Simulati
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B.1 Simulations of Nonlinear Optica
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C.2 Computation of V υ m(υ) in th
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C.3 Computation of V ξ m where rec
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C.5 Force in the Poisson 2D for Sma
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D.2 Conference Papers A. Alberucci
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References [1] E. Fermi, J. Pasta,
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REFERENCES [22] H. A. Haus and W. S
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REFERENCES [43] C. Conti, G. Ruocco
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REFERENCES [62] B. Zeldovich, N. Pi
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REFERENCES [83] Z. Xu, Y. V. Kartas
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REFERENCES [102] L. M. Blinov, G. C
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Solitons in Nonlocal Media

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