Nanostructured Anti-Reflection Coatings for Enhancing Transmission of Light

Abstract

Nanostructured, sub-wavelength anti-reflection layers (NALs) have attracted much attention as a new generation of anti-reflection surfaces. Among different designs, sub-wavelength periodic nanostructures are capable of enhancing transmission of coherent light through an interface without inducing scattering. In this work, we have explored a new profile for periodic NALs capable of transmitting IR light with higher efficiency compared to NALs based on a parabolic profile. To achieve high transmission and low diffraction, the profile and pitch of the nanostructured NALs are calculated using a combination of a multi-layer modeling and Rigorous Coupled Wave (RCWA) analysis.available materials with desired refractive indexes. Also, the mismatch between the thermal expansion coefficients of different layers, introduces residual stresses under high power illumination (this is a serious limitation for mechanical stability [6], and for applications like high power laser transmission particularly in the infrared where thicker layers are required) [7] [8].Nanostructured ARC layers (NALs [9]) on the other hand, work by a gradual, adiabatic change of effective refractive index from that of the incidence medium (air) to that of the bulk material (silicon in our case). These structures are also referred as moth-eye structures [10] due to their resemblance to the surface of a moth's eye [11]. In this paper, we will refer to nanostructures designed for re-

Optimizing Motheye Nanostructures and Achieving 100% Transmission

“…In this section, we have investigated multiple profiles for periodic nanostructures to reach 100% transmission. In our previous work, we investigated profiles which generated over up to 99.1% for a height equal to π phase shift [6]. Here, we find the profiles for maximal transmission of light, even superior to the previous profiles [6].…”

“…In our previous work, we investigated profiles which generated over up to 99.1% for a height equal to π phase shift [6]. Here, we find the profiles for maximal transmission of light, even superior to the previous profiles [6]. The heights of NALs will generate the same phase shift in the transmitted electromagnetic waves for a fair comparison.…”

“…Also, when a high-power beam of light passes through them, these layers peel off the substrate [5] due to the difference in the expansion coefficient of different materials. Recently, nanotechnology and nanostructures [6] [7] [8] [9] have solved many problems in technology introducing materials [10] that exhibit special characteristics electrically, mechanically [11]- [15] and when they're under illuminations of light [6] [7] [16] [17]. Fabrication method of these nanomaterials [6] [18] [19] usually depends on the type of the materials and the physical characteristics they're designed for.…”

“…NALs are the new generation of anti-reflection coatings designed to deal with previous problems [6]. These nanostructured materials are designed based on a fill factor concept [1].…”

“…NALs are used for different applications. For example, these structures can be used for increasing transmission in infrared detectors [26] or transmission of laser through different optical elements like lenses or polarizers [6] [17]. For solar cells and LEDs, the goal is to enhance scattering by eliminating total internal reflection or enhancing near-surface reflection by scattering light off normal [20] [21] [27].…”