A new method was proposed for the design of graded-refractive-index (GRIN) antireflective (AR) coatings with wide-angle and broadband characteristics. The gradient-index profiles of AR coatings were optimized using a genetic algorithm at a certain physical thickness. By applying optimized AR coating onto BK7 glass, the reflectance could be reduced to about 0.1 % for wavelength range covering 400 nm to 800 nm and incident angle from 0 to 80 degree. The optimization of step-graded GRIN AR coating was further investigated in detail, with a minimum refractive index of 1.1 which was able to be realized in our coating system. The average residual reflection reduced drastically with the increase of layer number. Sculptured AR coatings were deposited by electron beam evaporation with glancing angle deposition technology. Residual reflectances of the coating samples were in good agreement with theoretical calculations. Progresses on index optimization and deposition process would promote applications of structure engineered AR coatings, to meet both wide-angle and broadband requirements.
展开▼
