Subjects: Optics >> Quantum optics submitted time 2023-02-23
Hai Hu
Na Chen
Hanchao Teng
Renwen Yu
Yunpeng Qu
Jianzhe Sun
Mengfei Xue
Debo Hu
Bin Wu
Chi Li
Jianing Chen
Mengkun Liu
Zhipei Sun
Yunqi Liu
Peining Li
Shanhui Fan
F. Javier García de Abajo
Qing Dai
Abstract： Controlling the charge carrier density provides an efficient way to trigger phase transitions and modulate the optoelectronic properties in natural materials. This approach could be used to induce topological transitions in the optical response of photonic systems. Here, we predict a topological transition in the isofrequency dispersion contours of hybrid polaritons supported by a two-dimensional heterostructure consisting of graphene and $\alpha$-phase molybdenum trioxide ($\alpha$-MoO3). By chemically changing the doping level of graphene, we experimentally demonstrate that the contour topology of polariton isofrequency surfaces transforms from open to closed shapes as a result of doping-dependent polariton hybridization. Moreover, by changing the substrate medium for the heterostructure, the dispersion contour can be further engineered into a rather flattened shape at the topological transition, thus supporting tunable polariton canalization and providing the means to locally control the topology. We demonstrate this idea to achieve extremely subwavelength focusing by using a 1.2-$\mu$m-wide silica substrate as a negative refraction lens. Our findings open a disruptive approach toward promising on-chip applications in nanoimaging, optical sensing, and manipulation of nanoscale energy transfer.
Peer Review Status:
Awaiting Review
Subjects: Optics >> Quantum optics submitted time 2023-02-19
Hai Hu
Na Chen
Hanchao Teng
Renwen Yu
Mengfei Xue
Ke Chen
Yuchuan Xiao
Yunpeng Qu
Debo Hu
Jianing Chen
Zhipei Sun
Peining Li
F. Javier García de Abajo
Qing Dai
Abstract： Negative refraction provides an attractive platform to manipulate mid-infrared and terahertz radiation for molecular sensing and thermal radiation applications. However, its implementation based on available metamaterials and plasmonic media presents challenges associated with optical losses, limited spatial confinement, and lack of active tunability in this spectral range. Here, we demonstrate gate-tunable negative refraction at mid-infrared frequencies using hybrid topological polaritons in van der Waals heterostructures with high spatial confinement. We experimentally visualize wide-angle negatively-refracted surface polaritons on {\alpha}-MoO3 films partially decorated with graphene, undergoing planar nanoscale focusing down to 1.6% of the free-space wavelength. Our atomically thick heterostructures outperform conventional bulk materials by avoiding scattering losses at the refracting interface while enabling active tunability through electrical gating. We propose polaritonic negative refraction as a promising platform for infrared applications such as electrically tunable super-resolution imaging, nanoscale thermal manipulation, and molecular sensing.
Peer Review Status:Awaiting Review
Subjects: Biology >> Ecology submitted time 2017-11-17
Hui Xie
Saogao Zeng
Lili Zeng
Xiaobing Lan
Guicheng Zhang
Li Liu
Xin Lu
Na Chen
Zhiyuan Li
Zengzhao Tu
Hongjiang Xu
Ling Yang
Xiquan Zhang
Wenhui Hu
Abstract： Followed pharmacological evaluation exposed an extensive hepatic first pass effect within our recently disclosed DPP-IV inhibitors bearing thienopyrimidine scaffold. Through scaffold replacement with pyrrolopyrimidine, compound 1a had substantially improved the metabolic stability (from 6.6% to 65.07%), yet with severely poor absorptive property. Further modification by incorporation with varied substituents and structure conversion yielded both permeable and metabolic stable compounds. The whole pharmacokinetic- property based optimization had succeeded in balancing overall properties and resulted in the compound 1j, that with excellent efficacy to be a potential anti-diabetic candidate.
Peer Review Status:Awaiting Review
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