Improving antireflection in near-infrared wavelength range by double-sided planar coating on common substrates

Lowering the extent of unwanted reflection from the top surface of devices is essential for achieving higher efficiency. Reduction of reflection in the near-infrared range is experimentally demonstrated using dual-side coatings on different substrates with commonly available coating materials, with triple-layer coating on one side of the substrate and single-layer coating on the rear side. The extent of this reduction over a broad spectrum of more than 600 nm due to rear-side coating is evident from the analysis of four different substrates, with the effect being more pronounced for thinner substrates. The simulations suggest that the choice of the material for rear-side coating should be necessarily the one whose refractive index is less than that of the substrate, in order to reduce the reflection. A rear-side coating with silica of one quarter-wave thickness was capable of reducing reflection further in all the cases studied here, and the best antireflection was obtained for the substrate which has the largest refractive index variation with the rear-side coating material.