Binary subwavelength relief structures for infrared antireflection

Based on the effective medium theory, the antireflection properties of peri odic subwavelength surface-relief structures were analyzed and investigated . An estimation method for effective optical index for 2-D symmetric struct ures was given. Based on the consideration of feature size, the design conc ept of ridges and meshes was suggested. A two-dimensional infrared antirefl ection relief pattern was fabricated on a Si wafer, using ion beam etching process. From experimental results, it was shown that the structures, of wh ich the characteristics are similar to that of a single antireflection film , obviously suppressed the reflection in infrared spectrum, and its effecti ve refractive index is equivalent to the refractive index of the film. And the etching depth is equivalent to the thickness of 1/4 wavelength of the f ilm.