Design and performance of stealth film in near/mid-infrared bands compatible with laser at 1.06 and 1.54 microns

In view of the technical problems of long number of cycles and large total film thickness of stealth photonic crystal film in infrared bands compatible with laser, metal photonic crystals with defects were designed, and a method to reduce the layer number and thickness of stealth film in infrared bands compatible with laser was explored. In this paper, stealth materials in near/mid-infrared bands compatible with laser at 1060 and 1540 nm were designed by introducing defects in metal photonic crystal film. Take advantage of the small dispersion of metal K in the infrared, metal K-based photonic crystals were used to realize the multi- spectral digging holes at 1060 and 1540 nm. COMSOL was used to investigate the effects of dielectric refractive index, number of cycles, and film thickness of the defect layer on spectral performance in near (750–1400 nm)/mid-infrared (3000–5000 nm) bands. The results show that with the increase in dielectric refractive index, the defect mode narrows, and the reflectivity of the defect mode decreases accordingly, but the defect mode still remains at the wavelength of 1 060 nm and 1540 nm. In the near/mid-infrared bands, the reflectance is high. With the increase in the number of cycles, the number of defect modes increases correspondingly, and the width of the band gap narrows. With the decrease in the film thickness of the defect layer, the number of defect modes decreases. With the increase in the film thickness of the defect layer, the number of reflection valleys increases correspondingly, and the width narrows, and the minimum reflectivity also changes accordingly. Compared with dielectric photonic crystals, the ZnSe-K one-dimensional (1D) metal photonic crystals optimized in this paper have fewer film layers (4 layers), wide reflection bands (covering near/mid-infrared bands), and low reflection at both 1060 nm and 1540 nm, with the structure characterized by symmetry, short number of cycles, thinner total film layer number and compatibility of both two kinds of lasers. This research provides a theoretical basis for the application of metal photonic crystals to laser and stealth in infrared bands.