Discrete spatio-temporal dynamics in waveguide arrays with cubic nonlinearity

具有三次非线性的波导阵列中的离散时空动力学

• 批准号: 41018172
• 负责人: Professor Dr. Hartmut Bartelt
• 金额: --
• 依托单位: Leibniz-Institut für Photonische Technologien (IPHT)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/41018172?language=en
• 关键词: Discrete; spatio; temporal; dynamics; waveguide

Within this project discrete optical properties in permanent one- and two-dimensional waveguide arrays under different spatio-temporal conditions will be investigated. Such systems show unique fundamental properties in temporal and spatial field propagation differing from conventional propagation in homogeneous spaces (e.g. specific soliton formation, light bullets, periodic motion of beams, "non-diffractive" beams). As a basis for these investigations two complementary concepts for realizing high precision multidimensional waveguide arrays are used. With intensive ultrashort laser pulses focused into bulk material a permanent refractive index change can be induced which allows the inscription of complex and flexibly shaped embedded array structures. With optical fibre technologies large arrays with long propagation lengths and even active (gain) properties become feasible. Such evanescently coupled waveguide arrays will be used as a model system to study spatio-temporal propagation under linear and nonlinear conditions. Our work will be organized in six work packages.Work package (a) will address the study of linear propagation in one- and two-dimensional waveguide arrays. A wide field of interest is the investigation of the propagation in finite arrays, where interactions with the array boundaries have to be taken into account yielding a variety of new and interesting effects such as field self-recovery caused by harmonic oscillation or the discrete Talbot effect. Another consequence is the existence of a so-called quasi-incoherent propagation, where mutually fully coherent sources excite a light distribution which is equivalent to a distribution caused by mutually incoherent sources. Another focus of this package is the investigation of the propagation in different topologies. Using waveguide arrays written by fs laser pulses opens the possibility to analyze a variety of systems which can only be hardly fabricated by other technologies. Two-dimensional arrays consisting of curved waveguides allow the introduction of linear potentials causing two-dimensional field recovery. Furthermore the evanescent coupling concerning the shape and the distance of the waveguides will be analyzed since the investigation of the coupling to the next but one waveguide is intended. An additional point in this work package is the influence of interfaces between waveguide arrays. The interaction with the boundaries gives a significant insight in the propagation behaviour of the evolving light in the arrays since the band structure changes abruptly at the interface yielding staggered and unstaggered localized modes, dependent of the transmissivity of the interface.In work package (b) the nonlinear spatial propagation in one- and two-dimensional waveguide arrays will be investigated. The interaction of the propagating light with artificial defects will be precisely analyzed. Local defects can be linear (e.g. omitted waveguides) but also purely nonlinear. This causes so-called soliton emission which will be a main point of this work package. Another focus is the investigation of the influence of the dimensionality and the topology of the arrays. Since the band structure is a function of the array geometry the excitation of solitons in different topologies requires different input peak powers. So the transition from pure planar to two-dimensional solitons will be analyzed. The focus in work package (c) will be on the investigation of networking and all-optical switching. Propagating light may be blocked by localization in a single waveguide. Therefore, a propagating pulse may be routed at a waveguide junction into a specific direction. This effect has not been experimentally observed before. However, fs laser written waveguides provide an ideal basis for the investigation of this phenomenon since the paths of the waveguides can be chosen in an arbitrary way.The next consequential step will be the investigation of spatio-temporal nonlinear propagation in work package (d). In this work package we will primarily use waveguide arrays in fibres since they provide extraordinary long coupling lengths which allow the investigation of temporal dynamics in discrete systems. The interplay of the anomalous dispersion, Kerr-nonlinearity and array diffraction yields spatio-temporal localized objects, so-called light bullets. For spatially discrete systems theoretical studies predict the stability of discrete-continuous light bullets, which are otherwise dynamically instable in continuous media. Such phenomena have not been experimentally observed before. Hence, they will be a main focus in our work.In work package (e) waveguide arrays with dissipative effects (gain) will be fabricated and analyzed. A main goal is in particular the experimental observation of dissipative localizations in the form of dissipative light bullets and discrete spatio-temporal similaritons. Besides the gain resulting from cladding pumping, locally concentrated gain by core pumping is a further field of research. A detailed understanding of field formation and propagation in such active waveguide arrays with gain would be also of great interest for new types of fibre laser structures.Our work will be completed by work package (f) that is devoted to waveguide arrays in LiNbO3. This material exhibits an extraordinary strong quadratic nonlinearity which is the base for the investigation of a variety of effects possible only in discrete quadratic media. Furthermore, waveguide arrays in LiNbO3 allow the investigation of the interaction of linear, second- and third-order nonlinear discrete propagation.

在该项目中，将研究不同时空条件下永久一维和二维波导阵列的离散光学特性。此类系统在时间和空间场传播方面表现出独特的基本特性，不同于均匀空间中的传统传播（例如特定的孤子形成、光弹、光束的周期性运动、“非衍射”光束）。作为这些研究的基础，使用了实现高精度多维波导阵列的两个互补概念。通过将密集的超短激光脉冲聚焦到块状材料中，可以引起永久的折射率变化，从而可以刻写复杂且形状灵活的嵌入式阵列结构。利用光纤技术，具有长传播长度甚至有源（增益）特性的大型阵列变得可行。这种渐逝耦合波导阵列将用作模型系统来研究线性和非线性条件下的时空传播。我们的工作将分为六个工作包。工作包（a）将研究一维和二维波导阵列中的线性传播。一个广泛的兴趣领域是研究有限阵列中的传播，其中必须考虑与阵列边界的相互作用，从而产生各种新的有趣的效应，例如由简谐振动或离散塔尔博特效应引起的场自恢复。另一个结果是存在所谓的准不相干传播，其中相互完全相干源激发的光分布相当于由相互不相干源引起的分布。该软件包的另一个重点是研究不同拓扑中的传播。使用飞秒激光脉冲写入的波导阵列为分析各种其他技术难以制造的系统提供了可能性。由弯曲波导组成的二维阵列允许引入线性电势，从而引起二维场恢复。此外，由于旨在研究与下一个波导的耦合，因此将分析与波导的形状和距离有关的渐逝耦合。该工作包中的另一点是波导阵列之间的界面的影响。与边界的相互作用对阵列中不断变化的光的传播行为提供了重要的了解，因为能带结构在界面处突然变化，产生交错和非交错的局域模式，具体取决于界面的透射率。在工作包（b）中，将研究一维和二维波导阵列中的非线性空间传播。将精确分析传播光与人造缺陷的相互作用。局部缺陷可以是线性的（例如省略的波导），也可以是纯非线性的。这会导致所谓的孤子发射，这将是该工作包的要点。另一个重点是研究阵列的维数和拓扑的影响。由于能带结构是阵列几何形状的函数，因此不同拓扑中孤子的激发需要不同的输入峰值功率。因此将分析从纯平面孤子到二维孤子的转变。工作包 (c) 的重点将是网络和全光交换的研究。传播的光可能会被单个波导中的定位所阻挡。因此，传播脉冲可以在波导结处被路由至特定方向。这种效应以前从未在实验中观察到过。然而，飞秒激光写入波导为研究这种现象提供了理想的基础，因为波导的路径可以以任意方式选择。下一步将是研究工作包（d）中的时空非线性传播。在本工作包中，我们将主要使用光纤中的波导阵列，因为它们提供非常长的耦合长度，可以研究离散系统中的时间动力学。反常色散、克尔非线性和阵列衍射的相互作用产生了时空局部物体，即所谓的光弹。对于空间离散系统，理论研究预测离散连续光子弹的稳定性，否则在连续介质中动态不稳定。这种现象以前从未在实验中观察到过。因此，它们将成为我们工作的主要焦点。在工作包（e）中，将制造和分析具有耗散效应（增益）的波导阵列。主要目标特别是对耗散光弹和离散时空相似形式的耗散定位进行实验观察。除了包层泵浦产生的增益之外，芯泵浦产生的局部集中增益也是进一步的研究领域。详细了解这种具有增益的有源波导阵列中的场形成和传播对于新型光纤激光器结构也将产生极大的兴趣。我们的工作将通过专门研究 LiNbO3 波导阵列的工作包 (f) 来完成。这种材料表现出极强的二次非线性，这是研究仅在离散二次介质中可能存在的各种效应的基础。此外，LiNbO3 波导阵列可以研究线性、二阶和三阶非线性离散传播的相互作用。