Fig. 1. (a) TAS of GZO crystal at different delay time; the shaded area corresponds to the wavelength range of response greater than half of maximum. (b) Modulation depth change at detection wavelength of 620 nm; the solid line is the theoretical fitting, and the shaded areas represent the on and off time. (c), (d) Normalized transmittance change of GZO crystal at different wavelengths with delay time in non-degenerate and degenerate conditions, respectively. In (a)–(c), the pump wavelength is 650 nm and the pump fluence is 6.62 mJ/cm²; in (d), the pump fluence is 1.25 mJ/cm².

Fig. 2. Modulation depth variation with detection wavelength (blue) and corrected TPA coefficient (β^′_ND) (red) of GZO crystal under excitation at (a) 450, (b) 650, (c) 700, and (d) 750 nm wavelengths.

Fig. 3. TPA coefficients at different probe wavelengths when the pump wavelengths are at (a) 450, (b) 650, (c) 700, and (d) 750 nm; the solid lines represent theoretical fits.

Fig. 4. (a) PL spectrum of GZO crystal and the inset shows the PL spectrum of intrinsic ZnO. (b), (c) The configuration coordinate diagram of Ga_Zn defects in GZO; the solid upward arrow represents the process of electron excitation from the valence band to the corresponding defect states, the solid downward arrow signifies the process of hole capture leading to PL, and the upward dashed arrows denote the resonant interaction between the pump light and probe light.