Inverse design for compact magneto-optics

现代世界的大部分依赖于使用光纤电缆的通信。这些本质上是长玻璃管，通过它们可以发送光脉冲，将信息从一端传递到另一端。在光纤电缆之前或之后对光进行过滤和操作，使光脉冲能够转换为人类可读的信息。与电子设备如何操纵电子类似，这种光操纵设备与光子一起工作，因此它们的设计和表征属于光子学领域。就像微型化极大地提高了电子产品的性能一样，随着尺寸的缩小，光子器件将变得越来越普遍。一种被证明特别难以缩小的光子元件是光隔离器，它允许光在一个方向上传播，但不能在另一个方向上传播。它们广泛用于光纤通信，并开始在自动驾驶汽车（激光雷达）中使用的物体检测系统中发挥作用。它们通常是用一类表现出磁光效应现象的材料建造的，这种现象可以被利用来实现单向传播。试图用同样的材料制造更小的设备遇到了严重的问题。这些主要与在微观尺度上非常精确地操纵磁光材料时遇到的一些实际问题有关。解决这个问题的方法是使用一种更适合在非常小的设备中使用的材料。一个明显的候选者是硅，因为计算机处理器现有的庞大基础设施意味着硅基制造非常先进。不幸的是，硅具有弱的磁光特性，因此似乎不适合用作光隔离器。这个项目将使用一种被称为逆向设计的技术来回避这个困难，在这种技术中，人从设计过程中移除。相反，计算机使用有效的算法来确定实现特定目标的最佳结构。这项技术已被证明可以显著提高各种设备在各种环境中的性能。在这个项目中，该团队将以这样一种方式应用该算法，设计高性能、小型化的光学隔离器将是最终结果。它们将足够小，可以内置到紧凑型光子设备中，例如提高光纤通信的性能或用于自动驾驶车辆的技术。

Much of the modern world relies on communication using fibre optic cables. These are essentially long tubes of glass through which pulses of light can be sent, transferring information from one end to the other. Filtering and manipulation of the light before or after the fibre optic cable enables the pulses of light to be converted to and from human-readable information. In an analogy with how electronic devices manipulate electrons, such light-manipulating devices work with photons, so their design and characterisation is the field of photonics. In the same way as miniaturisation has dramatically improved the performance of electronics, photonic devices will become more and more commonplace as their dimensions are reduced. One photonic component that has proved particularly difficult to shrink is the optical isolator, which allows light to propagate in one direction but not in the other. These are used extensively in fibre optical communication and are beginning to find a role in the object detection systems used in self-driving cars (LiDAR). They are typically built using a class of materials exhibiting a phenomenon known as the magneto-optic effect, which can be exploited to allow unidirectional propagation. Attempts to create smaller devices using the same materials have run into significant problems. These are mostly related to some practical issues encountered when very precisely manipulating magneto-optical materials at microscopic scales.A route around this is to use a material more suited to use in very tiny devices. An obvious candidate is silicon, as the vast existing infrastructure for computer processors means silicon-based manufacturing is very advanced. Unfortunately, silicon has weak magneto-optical properties, so it seems unsuitable for use as an optical isolator. This project will sidestep this difficulty using a technique known as inverse design, in which the human is removed from the design process. Instead, a computer uses efficient algorithms to determine an optimal structure to achieve a particular goal. This technique has been shown to dramatically increase the performance of all kinds of devices in various contexts. In this project, the team will apply the algorithm in such a way that designs for high-performance, miniaturised optical isolators will be the end result. These will be small enough to be built into compact photonic devices, improving for example the performance of fibre-optical communications or the technology used in automated vehicles.