Fig. 1. Measured permittivity of ITO and theoretical curve of the Drude model，the wavelength where the real part equals 0 is the ENZ wavelength^［21］

Fig. 2. Dispersion relations of the long-range SPP mode（ENZ mode，blue）and short-range SPP mode（red）in the ultrathin ENZ film^［53］

Fig. 3. Optical modulation of ENZ material based on the electro-induced charge accumulation^［64］ and its application in electro-optical modulation waveguides^［70］

Fig. 4. All-optical modulation of polarization state^［22］ and transmittance^{［19，20］} in ENZ photonic devices

Fig. 5. Nonlinear frequency conversion in ENZ materials and ENZ-metal hybrid devices^{［93，96，97，101］}

Fig. 6. Optical frequency shifting in time-varying ENZ materials^［110］，and nonlinear phase conjugation and negative refraction in time varying ENZ-metal hybrid structure^［116］