Advanced Photonics, Volume. 4, Issue 3, 036002(2022)

Observation of flat-band and band transition in the synthetic space Article Video

Guangzhen Li1,†, Luojia Wang1, Rui Ye1, Shijie Liu1, Yuanlin Zheng1,2, Luqi Yuan1,*, and Xianfeng Chen1,2,3,*
Author Affiliations
  • 1Shanghai Jiao Tong University, School of Physics and Astronomy, State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai, China
  • 2Shanghai Research Center for Quantum Sciences, Shanghai, China
  • 3Shandong Normal University, Collaborative Innovation Center of Light Manipulation and Applications, Jinan, China
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    Constructions of synthetic lattices in modulated ring resonators attract growing attention to interesting physics beyond the geometric dimensionality, where complicated connectivities between resonant frequency modes are explored in many theoretical proposals. We implement experimental demonstration of generating a stub lattice along the frequency axis of light, in two coupled ring resonators of different lengths, with the longer one dynamically modulated. Such a synthetic photonic structure intrinsically exhibits the physics of flat band. We show that the time-resolved band structure read-out from the drop-port output of the excited ring is the intensity projection of the band structure onto a specific resonant mode in the synthetic momentum space, where gapped flat band, mode localization effect, and flat-to-nonflat band transition are observed in experiments and verified by simulations. This work provides evidence for constructing a synthetic stub lattice using two different rings, which, hence, makes a solid step toward experimentally constructing complicated lattices in multiple rings associated with synthetic frequency dimensions.

    Video Introduction to the Article

    1 Introduction

    Synthetic dimensions in photonics have attracted broad interest in recent years.14 They promise new ways to study fundamental physical phenomena with exotic artificial connectivities59 and manipulate light in various ways,1018 pointing toward exploration of higher-dimensional physics, beyond three dimensions.1921 Among recent experimental achievements, different degrees of freedom of light, including arrival times of pulses,10,11 frequencies,2224 and modal dimensions,8 have been used to construct synthetic dimensions. Hence, a variety of novel physics have been demonstrated in synthetic dimensions, such as the photonic topological insulator,8 the Hall ladder with effective magnetic flux,25 the trajectory of dynamic band structures,26 and the topological funneling with non-Hermitian physics,27 physical models of which are hard to build in structures with only spatial dimensions.


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    Guangzhen Li, Luojia Wang, Rui Ye, Shijie Liu, Yuanlin Zheng, Luqi Yuan, Xianfeng Chen. Observation of flat-band and band transition in the synthetic space[J]. Advanced Photonics, 2022, 4(3): 036002

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    Paper Information

    Category: Research Articles

    Received: Feb. 11, 2022

    Accepted: May. 25, 2022

    Posted: May. 25, 2022

    Published Online: Jun. 23, 2022

    The Author Email: Yuan Luqi (, Chen Xianfeng (



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