Fig. 1. Complex refractive index and fitting curve of metals. (a) Refractive index of silver; (b) Refractive index of gold

Fig. 2. Complex refractive index of composite materials and silicon

Fig. 3. Structural schematic diagram of gradient doped materials

Fig. 4. Equivalent refractive index of media with different doping concentrations. (a) Real part of complex refractive index; (b) Imaginary part of complex refractive index

Fig. 5. Schematic diagram of simulation model

Fig. 6. Simulated absorption spectra of silver nanoparticles doped materials. (a) Reflectivity; (b) Transmissivity; (c) Absorptivity; (d) Absorption improvement effect

Fig. 7. Simulated absorption spectra of materials doped with different nano metal particles. (a) Reflectivity; (b) Transmissivity; (c) Absorptivity; (d) Absorption improvement effect