Fig. 1. Spectrum simulation of 1D-PC film. (a) Schematic diagram of 1D-PC film. (b) Simulation reflectance under different periodic layers of 1D-PC film. (c) Simulation transmittance under different incidence angles of 1D-PC film with a defect layer. The transmission peak is at 1500 nm when light is normal incidence. (d) Simulation transmittance under different periodic thicknesses of defective 1D-PC film and the shifts of transmission peaks from 0° to 60°. The two transmission peaks are at 1500 nm (red line) and 1800 nm (black line) when light is normal incidence, respectively. (e) Simulation of the variation of the transmission spectrum of defective 1D-PC film with curvature. The transmission peak is at 1500 nm when light is normal incidence. (f) Simulation of the variation of the transmission spectrum of defective 1D-PC film with curvature. The transmission peak is at 1800 nm when light is normal incidence.

Fig. 2. The fabrication method of flexible 1D-PC film. (a) The effect of dissolving As₃₀S₇₀ under different solvent ratios. (b) Alternately spin-coating As₃₀S₇₀ solution and PVA solution while (c) drying to obtain (d) the flexible 1D-PC film. (e) Peeling off the film with tape.

Fig. 3. Characterization of photonic bandgap spectrum of 1D-PC film prepared by spin-coating. (a) Reflectance with different periodic layers. (b) Cross-sectional SEM image of a nine-period 1D-PC film. (c) Reflection and transmission spectrum of a nine-period 1D-PC film and comparison with the simulated reflectance spectrum. (d) Reflectance under different incidence angle of 1D-PC films. (e) The reflectance spectrum of different samples is almost identical under the same parameters. (f) The comparison of the reflectance spectrum of the 1D-PC film before and after the transfer shows that there is not much difference, which proves that the film’s structure is not damaged. The inset shows that the film exhibits good flexibility after transfer.

Fig. 4. Characterization of 1D-PC film curvature sensor. (a) The transmission peak of 1D-PC films with a central wavelength of 1500 nm varies with the incident angle. (b) The transmission peak of 1D-PC films with a central wavelength of 1800 nm varies with the incident angle. (c) Schematic diagram of the set-up for measuring the curvature of 1D-PC films. (d) The relationship between the central wavelength of the transmission peak and the curvature. The initial central wavelength is 1500 nm. (e) The relationship between the central wavelength of the transmission peak and the curvature. The initial central wavelength is 1800 nm. (f) Curvature response of the defective 1D-PC films with 1500 nm and 1800 nm initial peaks.