Fig. 1. Schematic diagram of the structure of LVOF film

Fig. 2. Device for sample preparation. (a) Physical map of the sample stage; (b) physical map of the control unit

Fig. 3. Physical picture of the sample holder in the sample compartment

Fig. 4. Optical constants of TiO₂ and SiO₂. (a) Refractive index; (b) extinction coefficient

Fig. 5. Simulated spectra. (a) Simulated reflectance spectra of (SiO₂/TiO₂)³; (b) simulated transmittance spectra of the LVOF

Fig. 6. Measured transmittance spectra. (a) Theoretical simulated spectra and the measured transmission spectra of the as-prepared and annealed samples when the cavity layer thickness is 200 nm; (b) transmission spectra of the F-P resonant cavity device and LVOF with a cavity thickness of 290 nm

Fig. 7. Transmission spectra of the sample. (a) As-prepared; (b) annealed at 200 °C; (c) annealed at 300 °C; (d) annealed at 400 °C

Fig. 8. Resonance peak center wavelength versus sample position. (a) Transmission spectra of samples with different annealing temperatures; (b) transmission spectra of samples with different annealing times; (c) relationship between the resonance peak wavelength of the annealed samples and the position of the samples