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- ItemSteering Directional Light Emission and Mode Chirality through Postshaping of Cavity Geometry(Hoboke, NJ : Wiley, 2020) Wang, Jiawei; Tang, Min; Yang, Yue-De; Yin, Yin; Chen, Yan; Saggau, Christian Niclaas; Zhu, Minshen; Yuan, Xiaobo; Karnaushenko, Dmitriy; Huang, Yong-Zhen; Ma, Libo; Schmidt, Oliver G.Dielectric optical microcavities have been explored as an excellent platform to manipulate the light flow and investigate non‐Hermitian physics in open optical systems. For whispering gallery mode optical microcavities, modifying the rotational symmetry is highly desirable for intriguing phenomena such as degenerated chiral modes and directional light emission. However, for the state‐of‐the‐art approaches, namely deforming the cavity geometry by precision lithography or introducing local scatterers near the cavity boundary via micromanipulation, there is a lack of flexibility in fine‐adjusting of chiral symmetry and far‐field emission direction. Here, precise engineering of cavity boundary using electron‐beam‐induced deposition is reported based on rolled‐up nanomembrane‐enabled spiral‐shaped microcavities. The deformation of outer boundary results in delicate tailoring of asymmetric backscattering between the outer and inner rolling edges, and hence deterministically strong mode chirality. Besides, the crescent‐shaped high‐index nanocap leads to modified light tunneling channels and inflected far‐field emission angle. It is envisioned that such a localized deposition‐assisted technique for adjusting the structural deformation of 3D optical microcavities will be highly useful for understanding rich insights in non‐Hermitian photonics and unfolding exotic properties on lasing, sensing, and cavity quantum electrodynamics.
- ItemExperimental observation of Berry phases in optical Möbius-strip microcavities(London [u.a.] : Nature Publ. Group, 2022) Wang, Jiawei; Valligatla, Sreeramulu; Yin, Yin; Schwarz, Lukas; Medina-Sánchez, Mariana; Baunack, Stefan; Lee, Ching Hua; Thomale, Ronny; Li, Shilong; Fomin, Vladimir M.; Ma, Libo; Schmidt, Oliver G.The Möbius strip, a fascinating loop structure with one-sided topology, provides a rich playground for manipulating the non-trivial topological behaviour of spinning particles, such as electrons, polaritons and photons, in both real and parameter spaces. For photons resonating in a Möbius-strip cavity, the occurrence of an extra phase—known as the Berry phase—with purely topological origin is expected due to its non-trivial evolution in parameter space. However, despite numerous theoretical investigations, characterizing the optical Berry phase in a Möbius-strip cavity has remained elusive. Here we report the experimental observation of the Berry phase generated in optical Möbius-strip microcavities. In contrast to theoretical predictions in optical, electronic and magnetic Möbius-topology systems where only Berry phase π occurs, we demonstrate that a variable Berry phase smaller than π can be acquired by generating elliptical polarization of resonating light. Möbius-strip microcavities as integrable and Berry-phase-programmable optical systems are of great interest in topological physics and emerging classical or quantum photonic applications.
- ItemSingle “Swiss-roll” microelectrode elucidates the critical role of iron substitution in conversion-type oxides(Washington, DC [u.a.] : Assoc., 2022) Liu, Lixiang; Huang, Shaozhuan; Shi, Wujun; Sun, Xiaolei; Pang, Jinbo; Lu, Qiongqiong; Yang, Ye; Xi, Lixia; Deng, Liang; Oswald, Steffen; Yin, Yin; Liu, Lifeng; Ma, Libo; Schmidt, Oliver G.; Shi, Yumeng; Zhang, LinAdvancing the lithium-ion battery technology requires the understanding of electrochemical processes in electrode materials with high resolution, accuracy, and sensitivity. However, most techniques today are limited by their inability to separate the complex signals from slurry-coated composite electrodes. Here, we use a three-dimensional “Swiss-roll” microtubular electrode that is incorporated into a micrometer-sized lithium battery. This on-chip platform combines various in situ characterization techniques and precisely probes the intrinsic electrochemical properties of each active material due to the removal of unnecessary binders and additives. As an example, it helps elucidate the critical role of Fe substitution in a conversion-type NiO electrode by monitoring the evolution of Fe2O3 and solid electrolyte interphase layer. The markedly enhanced electrode performances are therefore explained. Our approach exposes a hitherto unexplored route to tracking the phase, morphology, and electrochemical evolution of electrodes in real time, allowing us to reveal information that is not accessible with bulk-level characterization techniques.
- ItemPerovskite Origami for Programmable Microtube Lasing(Weinheim : Wiley-VCH, 2021) Dong, Haiyun; Saggau, Christian Niclaas; Zhu, Minshen; Liang, Jie; Duan, Shengkai; Wang, Xiaoyu; Tang, Hongmei; Yin, Yin; Wang, Xiaoxia; Wang, Jiawei; Zhang, Chunhuan; Zhao, Yong Sheng; Ma, Libo; Schmidt, Oliver G.Metal halide perovskites are promising materials for optoelectronic and photonic applications ranging from photovoltaics to laser devices. However, current perovskite devices are constrained to simple low-dimensional structures suffering from limited design freedom and holding up performance improvement and functionality upgrades. Here, a micro-origami technique is developed to program 3D perovskite microarchitectures toward a new type of microcavity laser. The design flexibility in 3D supports not only outstanding laser performance such as low threshold, tunable output, and high stability but also yields new functionalities like 3D confined mode lasing and directional emission in, for example, laser “array-in-array” systems. The results represent a significant step forward toward programmable microarchitectures that take perovskite optoelectronics and photonics into the 3D era. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.