**Aperiodic-Order-Induced Multimode E**ff**ects and Their Applications in Optoelectronic Devices**

### **Hao Jing, Jie He, Ru-Wen Peng \* and Mu Wang**

National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China

**\*** Correspondence: rwpeng@nju.edu.cn

Received: 3 August 2019; Accepted: 20 August 2019; Published: 4 September 2019

**Abstract:** Unlike periodic and random structures, many aperiodic structures exhibit unique hierarchical natures. Aperiodic photonic micro/nanostructures usually support optical multimodes due to either the rich variety of unit cells or their hierarchical structure. Mainly based on our recent studies on this topic, here we review some developments of aperiodic-order-induced multimode effects and their applications in optoelectronic devices. It is shown that self-similarity or mirror symmetry in aperiodic micro/nanostructures can lead to optical or plasmonic multimodes in a series of one-dimensional/two-dimensional (1D/2D) photonic or plasmonic systems. These multimode effects have been employed to achieve optical filters for the wavelength division multiplex, open cavities for light–matter strong coupling, multiband waveguides for trapping "rainbow", high-efficiency plasmonic solar cells, and transmission-enhanced plasmonic arrays, etc. We expect that these investigations will be beneficial to the development of integrated photonic and plasmonic devices for optical communication, energy harvesting, nanoantennas, and photonic chips.

**Keywords:** quasiperiodic order; self-similarity; quasiperiodic photonic micro/nanostructures; fractal-like photonic micro/nanostructures; quasiperiodic or fractal-like plasmonic structures
