• Advanced Photonics Nexus
  • Vol. 4, Issue 3, 036012 (2025)
Yingdi Pan1, Lu Sun1,*, Jingchi Li1, Qiyao Sun1..., Pan Hu1, Songyue Liu1, Qi Lu1, Xiong Ni1, Xintao He2, Jianwen Dong2,* and Yikai Su1,*|Show fewer author(s)
Author Affiliations
  • 1Shanghai Jiao Tong University, State Key Lab of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai, China
  • 2Sun Yat-sen University, School of Physics, State Key Laboratory of Optoelectronic Materials and Technologies, Guangzhou, China
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    DOI: 10.1117/1.APN.4.3.036012 Cite this Article Set citation alerts
    Yingdi Pan, Lu Sun, Jingchi Li, Qiyao Sun, Pan Hu, Songyue Liu, Qi Lu, Xiong Ni, Xintao He, Jianwen Dong, Yikai Su, "Wavelength- and structure-insensitive on-chip mode manipulation based on the Thouless pumping mechanism," Adv. Photon. Nexus 4, 036012 (2025) Copy Citation Text show less
    Thouless pumping process in an RM-modeled silicon waveguide array. (a) Schematic of the coupled-waveguide array. (b) Band structure of the TM supermodes in an array of 30 waveguides with alternating widths. The black solid lines represent the bulk bands, whereas the red and blue solid lines represent the left and right edge states when z∈[0,1/4)∪(3/4,1]. (c) Mode profiles (|E|) of the supermodes at Points IA to VIIIA (Points IB to VIIIB) on the blue (red) curve in panel (b).
    Fig. 1. Thouless pumping process in an RM-modeled silicon waveguide array. (a) Schematic of the coupled-waveguide array. (b) Band structure of the TM supermodes in an array of 30 waveguides with alternating widths. The black solid lines represent the bulk bands, whereas the red and blue solid lines represent the left and right edge states when z[0,1/4)(3/4,1]. (c) Mode profiles (|E|) of the supermodes at Points IA to VIIIA (Points IB to VIIIB) on the blue (red) curve in panel (b).
    Mode conversions based on the topological waveguide array. (a) Schematic of the mode conversion region composed of the topological waveguide array. (b)–(d) Light propagation profiles (|Ey|) at 1550 nm for the (b) TM0-to-TM1, (c) TM0-to-TM2, and (d) TM0-to-TM3 mode conversions when the TM0 mode is launched from the bottom narrow waveguide. (e)–(g) Simulated transmission spectra of different modes at the output ends of the (e) TM0-to-TM1, (f) TM0-to-TM2, and (g) TM0-to-TM3 coupling regions in panels (b)–(d).
    Fig. 2. Mode conversions based on the topological waveguide array. (a) Schematic of the mode conversion region composed of the topological waveguide array. (b)–(d) Light propagation profiles (|Ey|) at 1550 nm for the (b) TM0-to-TM1, (c) TM0-to-TM2, and (d) TM0-to-TM3 mode conversions when the TM0 mode is launched from the bottom narrow waveguide. (e)–(g) Simulated transmission spectra of different modes at the output ends of the (e) TM0-to-TM1, (f) TM0-to-TM2, and (g) TM0-to-TM3 coupling regions in panels (b)–(d).
    Comparison of the topological and conventional mode-order conversions. (a)–(f) Simulated transmission of the target modes (TM1−TM3) at 1550 nm when (a)–(c) the waveguide width deviation δw varies from −100 to 200 nm, or (d)–(f) the gap distance deviation δg varies from −100 to 150 nm. (g)–(i) Simulated transmission spectra of the target modes in different mode-order converters. The left, middle, and right columns of the figure correspond to the TM0-to-TM1, TM0-to-TM2, and TM0-to-TM3 conversions, respectively.
    Fig. 3. Comparison of the topological and conventional mode-order conversions. (a)–(f) Simulated transmission of the target modes (TM1TM3) at 1550 nm when (a)–(c) the waveguide width deviation δw varies from 100 to 200 nm, or (d)–(f) the gap distance deviation δg varies from 100 to 150 nm. (g)–(i) Simulated transmission spectra of the target modes in different mode-order converters. The left, middle, and right columns of the figure correspond to the TM0-to-TM1, TM0-to-TM2, and TM0-to-TM3 conversions, respectively.
    Structures of the fabricated devices. (a) Optical microscope photo of the fabricated MDM device. The correspondence between the ports and the modes is indicated in the figure. The TM0-to-TM1, TM0-to-TM2, and TM0-to-TM3 mode conversion regions are encircled by the red, green, and blue dashed boxes, respectively. (b)–(d) SEM images of the (b) TM0-to-TM1, (c) TM0-to-TM2, and (d) TM0-to-TM3 mode-order converters based on the topological waveguide arrays. (e)–(g) SEM images of the (e) TM0-to-TM1, (f) TM0-to-TM2, and (g) TM0-to-TM3 mode-order converters based on the conventional ADCs.
    Fig. 4. Structures of the fabricated devices. (a) Optical microscope photo of the fabricated MDM device. The correspondence between the ports and the modes is indicated in the figure. The TM0-to-TM1, TM0-to-TM2, and TM0-to-TM3 mode conversion regions are encircled by the red, green, and blue dashed boxes, respectively. (b)–(d) SEM images of the (b) TM0-to-TM1, (c) TM0-to-TM2, and (d) TM0-to-TM3 mode-order converters based on the topological waveguide arrays. (e)–(g) SEM images of the (e) TM0-to-TM1, (f) TM0-to-TM2, and (g) TM0-to-TM3 mode-order converters based on the conventional ADCs.
    Measured transmission spectra of the four modes when the light is injected from the (a) TM0, (b) TM1, (c) TM2, and (d) TM3 input ports of the proposed topological MDM device.
    Fig. 5. Measured transmission spectra of the four modes when the light is injected from the (a) TM0, (b) TM1, (c) TM2, and (d) TM3 input ports of the proposed topological MDM device.
    Measured transmission of the target modes at 1550 nm of the fabricated topological and conventional mode-division multiplexers with various fabrication errors. (a)–(c) Measured transmission of the (a) TM1, (b) TM2, and (c) TM3 modes when the waveguide width deviation δw varies from −90 to 90 nm. (d)–(f) Measured transmission of the (d) TM1, (e) TM2, and (f) TM3 modes when the gap distance deviation δg varies from −90 to 90 nm.
    Fig. 6. Measured transmission of the target modes at 1550 nm of the fabricated topological and conventional mode-division multiplexers with various fabrication errors. (a)–(c) Measured transmission of the (a) TM1, (b) TM2, and (c) TM3 modes when the waveguide width deviation δw varies from 90 to 90 nm. (d)–(f) Measured transmission of the (d) TM1, (e) TM2, and (f) TM3 modes when the gap distance deviation δg varies from 90 to 90 nm.
    High-speed data transmission experiment based on the four-channel topological MDM device. (a) Setup for the 200-Gb/s high data rate–transmission experiment. The black and orange lines represent optical and electrical links, respectively. (b) DSP algorithms for the transceivers. (c) Measured optical spectra for the 16-QAM signals at different stages. (d) BERs for the four signal channels. (e) Recovered constellations for each mode.
    Fig. 7. High-speed data transmission experiment based on the four-channel topological MDM device. (a) Setup for the 200-Gb/s high data rate–transmission experiment. The black and orange lines represent optical and electrical links, respectively. (b) DSP algorithms for the transceivers. (c) Measured optical spectra for the 16-QAM signals at different stages. (d) BERs for the four signal channels. (e) Recovered constellations for each mode.
    Mode-order conversionw1¯ (nm)Δw1 (nm)w2¯ (nm)Δw2 (nm)g (nm)Δg (nm)L (μm)
    TM0-to-TM1420[−30, 30]1110[−45, 45]300[−170, 170]80
    TM0-to-TM2420[−45, 45]1770[−81, 81]340[−180, 180]150
    TM0-to-TM3420[−35, 35]2450[−63, 63]385[−200, 200]200
    Table 1. Design parameters for different mode-order conversions.
    Ref.StructureBandwidth (nm)IL (dB)CT (dB)Fabrication tolerance
    4Shortcuts to adiabaticity100<1.3<−23±20 nm
    5ADCs20<4<−23
    32Directional couplers with subwavelength sidewall corrugations50<4<−16±20 nm
    33Tilt waveguide junctions with shallow etched slots60<1.29<−14.4
    34Pixelated waveguides60<3<−14.6±10 nm
    35Subwavelength grating-assisted triple-waveguide couplers100<5<−10±20 nm
    36Tapered ADCs75<6<−16±20 nm
    This workTopological waveguide arrays using the Thouless pumping mechanism80<2.6<−20.5±70 nm
    Table 2. Comparison of various silicon-based four-channel MDM systems.
    Yingdi Pan, Lu Sun, Jingchi Li, Qiyao Sun, Pan Hu, Songyue Liu, Qi Lu, Xiong Ni, Xintao He, Jianwen Dong, Yikai Su, "Wavelength- and structure-insensitive on-chip mode manipulation based on the Thouless pumping mechanism," Adv. Photon. Nexus 4, 036012 (2025)
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