Research on the 1.06 μm reflectivity of subwavelength surface-relief structure via finite different time domain method

In this paper, setting 1.06 um Gaussian modulated pulse electromagnetic wave as irradiation sources, the influences of structural parameters on reflectivity are analyzed by finite different time domain (FDTD) method. The results show that the filled factor and height are key factors for circular tube relief structure with non absorption. The optimal height could be set to 0.2 um, which is one odd time of the ratio of incident wavelength λ and four equivalent refractive index 4N, then the best filled factor is between 0.7 and 0.9, the ratio of inner and outer diameter could be set between 0.4 and 0.6, and the structure period has little significant influence. Compared with cylinder solid structure, it has been discovered that circular tube hollow structure could weaken the backward energy of electromagnetic wave, and it would be more suitable for antireflection structure than solid cylinder structure. Moreover, we design two another circular tube relief structures simulations with different extinction coefficients, it is found that the reflectivities are lower up to 0.00016% than the non absorption one.