Fig. 1. (a) Structural colors of microgratings written in AS glass with diverse periods (4.0–2.8 µm) under white light irradiation. (b) Optical micrograph of a grating with d of 3.0 µm. (c) The diffraction band behind the glass of (b) with white light irradiation.

Fig. 2. (a) Diffraction spectra of samples with different d irradiated by white light vertically measured at θ = 20°. (b) Fitting curve of d and the corresponding λ in (a). (c) CIE1931 chromaticity diagram for the spectra in (a). (d) Diffraction spectra of a sample with d = 2.0 µm irradiated by white light vertically measured at altering θ. (e) Fitting curve of sinθ and λ in (d). (f) CIE1931 plot for the spectra in (d).

Fig. 3. Optical micrographs of 4 µm microgratings with 4 µJ laser energy inside AS glass (a) before and (b) after heat treatment at 750°C for 2 h. The insets at the top right in (a) and (b) represent the structural color observed at θ = 20° under white light, which are both 1 mm × 1 mm. (c) Raman spectra of (b), with AS glass and the microgratings written by diverse laser energy.

Fig. 4. Apply this technique to printing colorizing patterns. Schematic diagrams of (a) Huawei icon and (b) BIT logo. (c) Huawei icon and (d) BIT logo inside AS glass photographed under white light from different incident angles.

Fig. 5. (a) Two QR codes with different information, which are “ZJU” and “BIT” written in perpendicular directions. (b) Colorizing patterns of QR codes in (a) are selectively displayed in the same region with incident light from diverse angles. The patterns are of the dimension 4.2 mm × 4.2 mm.