Time-asymmetric loop around an exceptional point over the full optical communications band
Time-asymmetric loop around an exceptional point over the full optical communications band
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DOI：
10.1038/s41586-018-0523-2
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发表时间：
2018-10-04
期刊：
影响因子：
64.8
通讯作者：
Berini, Pierre
中科院分区：
文献类型：
--
作者：
Yoon, Jae Woong;Choi, Youngsun;Berini, Pierre
在高耗散微波传输(3)和低温光学机械振荡器(4)实验中，围绕例外点(1-8)的拓扑运算--与非厄米特奇点相关的时变系统配置--已被建议作为实现深远的开放系统动力学的稳健方法。与基于闭合系统厄米动力学的传统系统形成鲜明对比的是，在特异点上的环境干扰与其内部耦合特性动态地结合在一起，在虚拟参数域中产生旋转刺激，导致手性系统表现出各种反常的物理现象(9-16)。为了实现新的波特性和相应的设备架构来控制它们，下一步是在应用广泛的技术领域实现这种系统，包括通信和信号处理系统。然而，目前还不清楚非厄米相互作用方案是否可以配置在强大的技术平台上，以用于进一步的设备工程。在这里，我们实验演示了一种具有光子模式的健壮的硅光子结构，该光子模式在光域中的一个例外点周围通过时间不对称环路传输。该结构由两个耦合的硅沟道波导和一个平板波导泄漏辐射宿组成，它精确地控制光子模所经历的非厄米哈密顿量。制造的器件在覆盖整个光学电信窗口(波长在1.2至1.675微米之间)的极宽频带上产生时间不对称的光传输。因此，利用具有可控光电特性的半导体平台，我们向基于非厄米拓扑动力学的宽带片上光学器件迈出了一步，并向一些潜在的实际应用迈进了一步，例如片上光隔离器和非互易模式转换器。我们的结果进一步表明，非厄米波动力学在其他物理学分支，如声学、凝聚态物理和量子力学中具有技术相关性。
Topological operations around exceptional points(1-8)-time-varying system configurations associated with non-Hermitian singularities-have been proposed as a robust approach to achieving far-reaching open-system dynamics, as demonstrated in highly dissipative microwave transmission(3) and cryogenic optomechanical oscillator(4) experiments. In stark contrast to conventional systems based on closed-system Hermitian dynamics, environmental interferences at exceptional points are dynamically engaged with their internal coupling properties to create rotational stimuli in fictitious-parameter domains, resulting in chiral systems that exhibit various anomalous physical phenomena(9-16). To achieve new wave properties and concomitant device architectures to control them, realizations of such systems in application-abundant technological areas, including communications and signal processing systems, are the next step. However, it is currently unclear whether non-Hermitian interaction schemes can be configured in robust technological platforms for further device engineering. Here we experimentally demonstrate a robust silicon photonic structure with photonic modes that transmit through time-asymmetric loops around an exceptional point in the optical domain. The proposed structure consists of two coupled silicon-channel waveguides and a slab-waveguide leakage-radiation sink that precisely control the required non-Hermitian Hamiltonian experienced by the photonic modes. The fabricated devices generate time-asymmetric light transmission over an extremely broad spectral band covering the entire optical telecommunications window (wavelengths between 1.26 and 1.675 micrometres). Thus, we take a step towards broadband on-chip optical devices based on non-Hermitian topological dynamics by using a semiconductor platform with controllable optoelectronic properties, and towards several potential practical applications, such as on-chip optical isolators and non-reciprocal mode converters. Our results further suggest the technological relevance of non-Hermitian wave dynamics in various other branches of physics, such as acoustics, condensed-matter physics and quantum mechanics.