Optical vortices in nonlocal nonlinear media

在电信系统中使用光来传输信号现在是无处不在的，事实上，如果不使用光纤中的激光进行传输，电信系统将会崩溃。充分利用在电信系统中使用光所带来的大量增加的容量机会的一个主要缺点是，用于处理信号的大多数电子设备仍然没有光学等价物。光等效信号的缺乏给电信网络带来了瓶颈，因为电处理比光处理慢，部分原因是需要在光信号和电信号之间切换，然后再切换回光信号。一个主要的科学和工程问题是设计光学等效的电信号处理设备。目前的提议处理一个这样的问题，即利用所谓的光涡流设计可重构电路。光涡旋可以形成光信号（孤子）传播的通道。由于这些漩涡可以在光学材料的任何地方和任何方向形成，因此它们可以被用作可以随意改变的电线的等量物。在使用这种光旋涡之前，需要解决一些基本问题，例如，这种光旋涡的哪些参数值和配置是稳定的？当这些涡旋受到扰动时，它们是如何演变的？在实验室中产生它们有多容易？众所周知，对于许多材料来说，由于这些材料没有远距离相互作用，光学涡流是不稳定的。所以我们需要的是具有长距离相互作用的材料。其中一种材料就是液晶。然后提出研究液晶中光学涡流的稳定性和演化，作为非局部材料中光学涡流演化的一个例子。这项研究的结果将用于在实验室中形成和研究光学涡流。

The use of light to transmit signals in telecommunication systems is now ubiquitous and, indeed, the telecommunications system would collapse without the use of laser light in optical fibres for transmission. A major drawback to fully utilising the vastly increased capacity opportunites presented by using light in telecommunication systems is that there are still no optical equivalents for most of the electronic devices used to process signals. This lack of optical equivalents presents a bottleneck in the telecommunication network in that electrical processing is slower than optical processing, in part due to the need to switch between opticsl to electrical, then back to optical signals. A major scientific and engineering problem is then to design optical equivalents to electrical signal processing devices. The present proposal deals with one such problem, the design of re-configurable circuits using so-called optical vortices. Optical vortices can form channels through which optical signals (solitons) can propagate. As these vortices can be formed anywhere and in any direction in an optical material, they then can be used as the equivalent of eletrical wires which can be changed at will. Before such optical vortices can be used, fundamental questions need to be addressed, such as for which parameter values and configurations are such optical vortices stable? How do such vortices evolve when they are perturbed? How easily can they be generated in the laboratory? It is known that for many materials, optical vortices are unstable due to these materials not having long range interactions. So what is needed is materials which possess long range interactions. One such material is a liquid crystal. It is then proposed to investigate the stability and evolution of optical vortices in liquid crystals as an example of such evolution in a non-local material. The results of this research will then be used to form and study optical vortices in the laboratory.