Fig. 1. (a) Optical micrograph of 4 µm×2.6 µm As₂S₃ snakes strip waveguide^[24]; (b) AFM picture of As₂S₃ waveguide sidewall roughness after thermal annealing^[25]; (c) Scanning Electron Microscopy (SEM) and cross-section of As₂₀S₈₀ disk resonator^[26]; (d) SEM and cross-section of As₂₀S₈₀ microring resonator^[27]; (e) Depositing the As₂S₃core material on the SiO₂ platform structure, and SEM of cleaved cross-section of waveguide^[28]

Fig. 2. (a) SEM cross-sectional view image of GeAsSe waveguide^[33]; (b) SEM image of a GeSbS microresonator^[36]; (c) SEM image of a Ge₂₈Sb₁₂Se₆₀ microdisk resonator^[37]; (d) SEM image of a Ge₂₈Sb₁₂Se₆₀ microring^[38]; (e) SEM top-view image of a suspended GeAsSe microdisk resonator^[33]; (f) Lorentzian fit to the resonance dip^[36]; (g) Lorentzian fit to the resonance dip at 1559.657 nm^[37]; (h) Lorentzian fit to the resonance dip^[38]

Fig. 3. (a) 200 μm radius microdisk resonator; (b) Simulated field intensity profile of the fundamental mode of the microdisk resonator^[22]; (c) SEM image of the cross-section of waveguide^[48]

Fig. 4. (a) Schematic diagram and SEM image of the Ge₂₃Sb₇S₇₀ spiral waveguide^[54]; (b) Cross-sectional view and the corresponding SEM image of the ridge waveguide comprising two different compositions of GeSeSe glasses^[61]; (c) Schematic diagram and cross-sectional SEM image of the the ZnSe rib waveguide^[63]; (d) Cross-sectional SEM image of the Ge₂₈Sb₁₂Se₆₀ strip waveguide and schematic diagram of the waveguide integrated with a PDMS gas cell^[56]; (e) Schematic diagram of the Ge₂₈Sb₁₂Se₆₀ waveguide sensor using the silver island film^[64]

Fig. 5. (a) Schematic, electric field distribution and band diagram of the Ge_11.5As₂₄Se_64.5 grating resonance sensor ^[68]; (b) SEM images of the Ge₂₈Sb₁₂Se₆₀ waveguide sensor using micro-ring resonance ^[70]; (c) SEM images of the Ge₂₈Sb₁₂Se₆₀ slot waveguide and the Ge₂₈Sb₁₂Se₆₀ slot micro-ring sensor ^[71]

Fig. 6. (a) Schematic diagram of on-chip SC integrated with optical sensor ^[39]; (b) Schematic diagram and cross-sectional view of the optical sensor using spiral waveguide integrated with PbTe photodetector ^[55]

Fig. 7. (a) Typical waveguide cross section under SEM inspection^[29]; (b) The simulation of supercontinuum spectrum broadening^[29]; (c) Experimental results of supercontinuum spectrum generation in TM mode^[29]; (d) Typical waveguide cross section under SEM inspection^[52]; (e) Experimental SC evolution with increasing powers at a pump wavelength of 4.184 μm^[52]

Fig. 8. (a) Overview of SBS: A pump wave (ω₁) scatters from and re-enforces an acoustic phonon (Ω) and is downshifted to a Stokes wave (ω₂), the result is a narrow Stokes peak separated at a distance of GHz from the pump, this configuration shows backward Brillouin scattering^[86]; (b) Schematic of a BL based on photonic chip^[82]; (c) Schematic of the hybrid As₂S₃ring resonator structure, concept figure for the lasing conditions^[84]; (d) SBS-based integrated microwave photonic filter, stopband center frequency tuning^[83]

Fig. 9. (a) Lorentzian fit to the resonance dip of As₂S₃ microsphere^[91]; (b) Raman emission power versus coupled pump power^[91]; (c) Image of a typical packaged As₂S₃ microsphere^[92]; (d) Lorentzian fit to the resonance dip of typical packaged As₂S₃ microsphere^[92]; (e) Spectrum of a 5 Raman orders cascaded SRS emission of an As₂S₃ microsphere^[92]; (f) Experimental spectrum of four-cascade Raman lasing^[85]; (g) Measured Raman spectrum when increasing the pump power to ~30 mW^[36]

Fig. 10. Integrated photonic chalcogenide phase-change switching. (a) Schematic of the integrated photonic SiN-on insulator platform for broadband switching operation^[102]; (b) Spectral shift and loss characterization of GST using silicon microring resonators^[103]; (c) Low-loss broadband directional coupler switches based on GST^[104]

Fig. 11. (a) Schematic of all-optical multi-level memory based on Si₃N₄ microring resonator^[106]; (b) Operation principle of an all-optical fully integrated on-chip multilevel memory; (c) A multibit and multiwavelength architecture^[96]

Fig. 12. PCM based optical VMM and neural networks: (a) A chip-scale all-optical abacus based on GST on Si₃N₄^[108]; (b) Photonic in-memory computing demonstrating optical scalar-scalar multiplication and matrix-vector multiplication^[110]; (c) An integrated photonic tensor core enabled by an optical frequency comb and in-memory computing cell arrays^[111]

Table 1. Current several typical chalcogenide waveguides at 1.55 µm

Table 2. Recent research progress of chalcogenide optical waveguide performance in mid-infrared band

Table 3. Research progress of on-chip mid-infrared SC output in chalcogenide waveguides