chapter  4
20 Pages

Modeling and Characterization of Nonlinear Optical Effects in Photonic Nanowires

WithRim Cherif, Mourad Zghal, Amine Ben Salem

Highly nonlinear optical waveguides have great interest for compact, low-power, and all optical nonlinear devices. Nonlinearity in waveguides can be enhanced either by modi- cations in the structure to reduce the effective mode area (Aeff) or by using materials with higher Kerr nonlinearity (n2). In fact, photonic nanowires with diameters smaller than the wavelength of the guided light attract considerable interest due to their unique properties and wide range of applications [1]. Tapering is a commonly used method for reducing optical ber dimensions and engineering the waveguide dispersion. Low-loss ber tapers with sub-wavelength waist diameters have been fabricated from both standard single-mode bers (SMFs) [1-3] and photonic crystal bers (PCFs) [3-5]. These structures

CONTENTS

4.1 Introduction ........................................................................................................................ 103 4.2 Photonic Nanowires .......................................................................................................... 104

4.2.1 Denitions and Concepts ..................................................................................... 104 4.2.2 Fabrication ............................................................................................................... 105 4.2.3 Applications ............................................................................................................ 106

4.3 Optical Characterization of Photonic Nanowires ......................................................... 107 4.3.1 Optical Modal Analysis ........................................................................................ 107

4.3.1.1 Air-Silica Nanowires ............................................................................. 107 4.3.1.2 Tapered Silica Photonic Crystal Fibers (TSPCFs) ............................... 110 4.3.1.3 Tapered Chalcogenide Fibers ................................................................ 111

4.4 Nonlinear Propagation...................................................................................................... 112 4.4.1 Soliton Self-Compression and Supercontinuum Generation

in Air-Silica Nanowires ........................................................................................ 113 4.4.1.1 Study of the Effect of the Input Pulse Shape and Duration .............. 113 4.4.1.2 Study of the Effect of the Photonic Nanowire Size ............................ 114 4.4.1.3 Study of the Effect of the Input Pulse Energy .................................... 116

4.4.2 Soliton Self-Compression and Supercontinuum Generation in As2Se3 Nanowires .............................................................................................. 117

4.5 Conclusion .......................................................................................................................... 118 References ..................................................................................................................................... 119

not only are platforms for microphotonic devices but also enable nonlinear process such as soliton-effect compression and supercontinuum (SC) generation at low input pulse energies [5,6]. The reduction in the effective mode area and the subsequent enhancement of the nonlinearity are ultimately limited by the index contrast of air and material (e.g., silica) in the case of SMFs [7], as well as the structural dimensions in the case of PCFs [8]. The pronounced evanescent eld surrounding the ber and the strong radial connement of the light [7] make nanobers well suited for an efcient and controlled interaction of the guided light with matter.