Research on Dielectric/Metal/Dielectric film system for high transmittance compatible laser stealth

The "cat's eye effect" in the optical window of all kinds of photoelectric equipment is the main basis of a laser active detection system, which poses a great threat to military equipment and combatants. However, under the condition of ensuring high visible transmittance, the sniper stealth scheme for anti-laser active detection remains to be discussed. In this paper, genetic algorithm was used to reverse design the metasurface anti-reflection film. Si3N4 and Ag were composed of three-layer anti-reflection film, and rectangular array of metal micro-nano structures were added on the top layer to form a wavelength selective absorber, so as to achieve the effect of low reflection and high absorption at laser wavelength. By combining the device design with genetic algorithm, the parameter combination that best meets the target performance of the device is obtained. The average transmittance at 380nm~780nm is 88% meanwhile the maximum transmittance peak of 94%. The reflectance at 1550nm of 10%, and the absorption rate of 80% are achieved. In order to better meet the requirements of practical application, we further designed the cross metal array to obtain polarization insensitive characteristics. The metasurface anti-reflective membrane with improved structure can achieve an average visible transmittance of 82% and a reflectance of 5% at 1550nm. The two metasurface anti-reflection film designed in this paper does not require additional devices, and the imaging quality can be guaranteed. At the same time, it can effectively reduce the laser echo energy, so as to achieve the effect of high quality visible light transmittance and laser stealth compatibility.