Iterative design of moth‐eye antireflective surfaces at millimeter wave frequencies

Abstract

A method for synthesizing broadband antireflective (AR) surfaces at millimeter wave frequencies is demonstrated. AR surfaces were formed by machining a multilayer subwavelength structures into nonabsorptive dielectrics. This created low‐reflected energies (<−25 dB) over large bandwidths and incidence angles. Experimental results are provided demonstrating the validity of the method. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 561–568, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24973

Numerical Modeling of Sub-Wavelength Anti-Reflective Structures for Solar Module Applications

“…RCWA has been used to model a large variety of periodic anti-reflective structures in three dimensions (which are considered two dimensional gratings). Most of the structures modeled with this method are hexagonally or square packed, GRIN, moth-eye-like nipple arrays [ 60 , 72 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 ] (see Figure 21 ) or, more specifically, tapered and truncated cones [ 84 , 85 , 86 , 87 ], nanocones and nanopillars [ 88 ], core/shell GRIN structures [ 89 , 90 ], and inverted moth eyes [ 67 ]. Many of these studies concentrated on designing the optimal period, height, or refractive index profile for the moth eye structures and some explored the effects of angles of incidence of the plane wave of light.…”

Design of graded index flat lenses with integrated antireflective properties

“…Recently, it was reported in Ref. 6 how broadband AR surfaces at microwave frequencies can be designed by drilling subwavelength cylindrical holes into a nonabsorptive dielectric substrate, shown in Figure 2. The surface structure was designed using a rigorous EM model and an iterative optimization algorithm.…”

“…It was noted in Ref. 6 that an exact surface geometry to achieve good AR performance was not unique. More specifically, it is possible to find multiple geometries (i.e., different hole depths, radii, and periodicities) that achieved comparable AR performance.…”

“…Our method uses an aperiodic subwavelength surface structure creating an “effective” index of refraction that varies spatially and, thus, can be used to realize GRIN lenses or other GRIN‐based optical elements. Other authors have demonstrated how aperiodic subwavelength surfaces can be used to create a spatial variation of effective dielectric properties (i.e., GRIN) [ 1–6]. This previous work was useful for creating flat optical elements, such as lenses, however, it did not account for loss in transmission due to front and back face reflections.…”

Effective properties of cylinders in a square lattice

“…The incident angle for this analysis is normal. The permittivity was derived using the method described in [4] with a rigorous coupled wave solution. The percent error was calculed by…”