Gauge‐Induced Floquet Topological States in Photonic Waveguides

Abstract

Tremendous efforts are devoted to the research of exotic photonic topological states, in which Floquet systems suggest new engineered topological phases and provide a powerful tool to manipulate the optical fields. Here, a gauge‐induced topological state localized at the interface between two gauge‐shifted Floquet photonic lattices with the same topological order is demonstrated. The quasienergy band structures reveal that these interface modes belong to the Floquet π modes, which are further found to enable an asymmetric topological transport of this interface mode thanks to the flexible control of the Floquet gauge. The intriguing propagations of the gauge‐induced topological states are experimentally verified in a silicon waveguides platform at near‐infrared wavelengths, which show broadband working wavelengths and robustness against the structural fluctuations. This work provides a new route in manipulating optical topological modes by Floquet engineering and inspires more possibilities in photonics integrations.

Broadband and Fabrication Tolerant Power Coupling and Mode‐Order Conversion Using Thouless Pumping Mechanism

“…This method has shown significant advantages in broadening the working bandwidth and loosening the fabrication requirement of coupledwaveguide devices. Our findings may pave the way to high-quality massive photonic integration, which would possibly boost progresses in on-chip information processing, [29][30][31] high-speed optical communications, [22] and integrated quantum photonics. [32,33] 2.…”

“…[29,30] In this paper, we present a theoretical and experimental study of broadband and fabrication tolerant power coupling and modeorder conversion enabled by the Thouless pumping mechanism in finite Rice-Mele (RM) modeled silicon photonic waveguide arrays. Contrary to the topological systems reported in previous works, [29,30] the adiabatic pumping scheme used in the RM model warrants that the designed devices are immune to the variations in wavelength, gap distance and waveguide width to a large extent. In our experiments, topological photonic directional couplers (DCs) and mode-order converters (MCs) were built on the silicon-on-insulator (SOI) platform along with their conventional counterparts.…”

“…However, the coupling is still vulnerable to the structural variation in waveguide width. [29,30] In this paper, we present a theoretical and experimental study of broadband and fabrication tolerant power coupling and modeorder conversion enabled by the Thouless pumping mechanism in finite Rice-Mele (RM) modeled silicon photonic waveguide arrays. Contrary to the topological systems reported in previous works, [29,30] the adiabatic pumping scheme used in the RM model warrants that the designed devices are immune to the variations in wavelength, gap distance and waveguide width to a large extent.…”

Topological Photonic States in Waveguide Arrays

“…The most straightforward applications involve topologically protected boundary states as high-performing photonic integration devices. [128][129][130] As shown in Figure 6a,b, the topological SSH waveguide arrays fabricated on magneto-optical materials can serve as optical isolators with much higher isolation ratios than any other on-chip isolator device types, due to the intrinsic nonreciprocity of the magneto-optic effect. [128] The same structure fabricated on a silicon substrate can be developed into a broadband optical coupler.…”

“…[128] The same structure fabricated on a silicon substrate can be developed into a broadband optical coupler. [130] Besides static waveguides, topological coupled-waveguide devices induced by artificial gauge field (AGF) and Thouless pumping mechanism exhibit more advantages, in terms of robustness against the variations in wavelength, waveguide spacing, and waveguide width (Figure 6c). [131][132][133] These predominant properties arise from the topological protection of the Chern number and the flat dispersion.…”