Fig. 1. (a) Schematic diagram of the principles and steps of inorganic modification and organic modification of VO₂ nanocrystal particles; (b-d) A single transmission electron microscope (TEM) picture of VO₂ nanocrystalline particles, (b) modified with aluminum oxide, (c) modified with titanium dioxide, (d) modified with silicon dioxide, and there is Al₂O₃ appearing as amorphous flocculent around the VO₂ lattice in (b). The scales are all 5 nm; (e) The comparison of dispersion characteristics of VO₂ nanocrystals before and after modification in water and dichloromethane solutions, where the left picture is without surface modification, the middle picture shows the dispersion properties after organic modification, and the right picture shows the dispersion properties after inorganic modification and organic modification; (f) SEM image of the photosensitive composite material with 20 wt% VO₂. The scale is 1 μm; (g) Calculated refractive index curves of 10 wt%, 20 wt%, 30 wt%, 40 wt% VO₂ nanocrystalline photosensitive composite materials before and after the phase transition with the rise of the temperature, where the left picture shows the data of the real part of the refractive index, and the picture on the right shows the data of the imaginary part of the refractive index. The solid line of dielectric represents the medium state before the phase transition with the rise of the temperature, and the metallic dotted line is the metalloid state after the phase transition with the rise of the temperature

Fig. 2. (a) Schematic diagram of the optical path of the femtosecond laser direct writing fabrication system. Among them, M is the mirror, L is the lens, Pinhole is the filter hole, Gx and Gy are the galvanometer system, BS is the beam splitter, and Objective is the objective lens; (b) XOZ surface optical field distribution of the laser focus spot; (c) Schematic diagram of the photonic device spectrum test device, which uses a ring-shaped ceramic heating plate connected to a DC power supply to heat the photonic device and uses an infrared temperature gun to test the temperature of photonic devices

Fig. 3. (a) SEM images of the single-line structures processed at different laser powers and scanning speeds, where the VO₂ concentration is 20 wt%; (b) Laser threshold power of the processed single-line structures at different scanning speeds based on 20 wt% VO₂ photosensitive composite materials. The laser threshold power is a function of the scanning speed; (c) The line width of the processed single-line structures changes with the power, where the scanning speed is 20 μm/s, the VO₂ concentration is 20 wt%, and the embedded figure is the laser power versus the polymerization rate

Fig. 4. (a) Schematic diagram of the three-dimensional layer stacking structure model; (b-d) The three-dimensional layer stacking structure processed based on 20 wt% VO₂ photosensitive composite material, where (b) is the optical microscope picture, (c) is the SEM picture, and (d) is the SEM oblique view; (e) Schematic diagram of the spiral icosahedral structure model; (f-h) Spiral icosahedral structure processed based on 20 wt% VO₂ photosensitive composite material, where (f) is the optical microscope image, (g) is the SEM image, and (h) is the SEM enlarged image

Fig. 5. (a) Pure photoresist-type one-dimensional grating; (b) Reflection spectra of pure photoresist-type one-dimensional grating device before and after heating, where the upper figure is the test data, and the lower figure is the simulated data; (c) 20 wt% VO₂ type one-dimensional grating; (d) Reflection spectrum of 20 wt% VO₂ type one-dimensional grating device before and after heating, where the upper figure is the test data, and the lower figure is the simulated data; (e) Distribution of the z component of the magnetic field in the XOZ plane of a single periodic 20 wt% VO₂ grating, where the upper picture shows the light source wavelength of 2.9 μm, and the lower picture shows the light source wavelength of 4.2 μm, the white dotted line is the cross-sectional profile of a single periodic grating structure; (f) 20 wt% VO₂ type woodpile structure; (g) Transmission spectra of pure photoresist woodpile structure before and after heating; (h) Transmission spectra of 20 wt% VO₂ type woodpile structure before and after heating, where the black line is 25 ℃, and the red line is 75 ℃