Periodic structures for nonlinear optics

非线性光学是用来描述光与物质相互作用的术语，其中相互作用的强度取决于光强度。本研究项目关注的非线性效应是基于高强度激光束引起的折射率变化的非线性效应。这种效应已被用于演示一系列全光开关和信号处理设备。然而，在大多数材料中存在的相对较小的非线性系数导致过高的光功率水平，并限制了此类器件的潜在应用。由于其新颖的光学特性，周期结构几十年来一直吸引着科学家和工程师。例如，在蛋白石晶体和蝴蝶翅膀中观察到的颜色是由于潜在的周期性结构，而不是色素沉着的结果。这种周期性结构的一个相关好处是，它们导致光的高度限制，从而使非线性光学相互作用更有效。需要克服的挑战是设计周期结构，以增强非线性光相互作用，并在长期内产生实用的全光开关和信号处理设备。该应用的目的是将当前和正在开发的非线性材料与工程、周期光子结构相结合，以展示新颖的全光学功能。此外，还将对光学增益的使用进行研究，以期进一步降低对光功率的要求。

Nonlinear optics is the term used to refer to the interaction of light and matter where the strength of the interaction depends on the optical intensity. The nonlinear effects of interest in this research program are those based on the change in refractive index induced by a high intensity laser beam. Such effects have been used to demonstrate a range of all-optical switching and signal processing devices. However, the relatively small nonlinear coefficients present in most materials result in prohibitively high optical power levels and limit the potential applications of such devices. Periodic structures have fascinated scientists and engineers for decades because of their novel optical properties. For example the colors observed in opal crystals and butterfly wings are due to the underlying periodic structures and not a consequence of pigmentation. One of the associated benefits of such periodic structures is that they lead to a high degree of confinement for light and as a result make nonlinear optical interactions more efficient. The challenge to be overcome is to engineer periodic structures which will enhance nonlinear optical interactions and which in the long term will result in practical all-optical switching and signal processing devices. The aim of this application is to combine current and developing nonlinear materials with engineered, periodic photonic structures to demonstrate novel all-optical functionalities. In addition, the use of optical gain is such periodic structures will  be investigated with a view to further reducing the optical power requirements.