Numerical study on laser and infrared compatible stealth by forming "hole-digging spectrum" of doped photonic crystal

Abstract

Compatible stealth of laser and infrared is an urgent demand of modern battlefield, but the demand is ambivalent for conventional materials. As a new type of artificial structure function material, photonic crystals can realize broadband thermal infrared stealth based on its high-reflection photon forbidden band. By forming a "hole-digging" reflection spectrum of doped photonic crystals, high transmittance at military laser wavelength of 1.06μm and 10.6μm can be achieved, so compatible stealth of laser and infrared can be achieved too. In this paper, we selected middle and far infrared-transparent materials, PbTe and Na₃AlF₆ as high refractive index and low refractive index material respectively, and designed a one-dimensional two-defect-mode photonic crystal based on principles of distributed Bragg reflector microcavity. And then its photon forbidden band was broaden to 1~20μm by constructing two heterojunction photonic crystals. The reflection spectrum and transmission spectrum of the photonic crystals were calculated by characteristic matrix method of thin-film optical theory. The calculation results show that the designed multi-cycle dual-heterojunction photonic crystal has a high spectral reflectance in the near, middle and far infrared band, whose spectral reflectivity is greater than 99% in 1~5μm and 8~14μm infrared bands, and spectral transmittance at 1.06μm and 10.6μm is greater than 96%. This will satisfy the laser and infrared compatible stealth in the near, middle and far infrared bands.