Antireflection structured surfaces for the infrared spectral region

Abstract

Antireflection structured (ARS) surfaces on GaAs substrates for application with normally incident, randomly polarized, 10.6-microm-wavelength radiation are designed and analyzed. Both one-dimensional (1-D) and two-dimensional (2-D) multilevel profiles are examined with special attention given to multilevel approximations of 1-D triangular and 2-D pyramidal profiles. The 1-D profiles are designed by using second-order effective medium theory (EMT), as we have found zeroth-order EMT to be insufficient when ARS surfaces are designed for use with optically dense materials, e.g., most materials used in the infrared spectral region. We analyze both 1-D and 2-D profiles by using rigorous coupled-wave analysis and find that the more levels the profile contains, the better the ARS surface's response to bias angles, wavelength detunings, and errors in etch depth. Although both 1-D and 2-D profiles can efficiently suppress reflections for unpolarized light, 2-D gratings are advantageous when randomly polarized light is of interest.

A broadband micro-machined far-infrared absorber

“…For λ ≫ p the effective relative dielectric function,ǫ r (ζ), is quasi-static and computed from the silicon volume filling fraction for the unit cell in the mean field approximation. 17 The dielectric losses arising from the silicon taper volume are readily treated within this framework.…”

“…The approach is conceptually motivated by moth-eye anti-reflection coatings [14][15][16][17] and analogous microwave terminations. 18 Details of the meta-material's controlling parameters, fabrication, and characterization are provided in Sections II III, and IV respectively.…”

Nanohot embossing using curved stage to replicate antireflection nanostructures onto light guide

“…Therefore, the height of nanostructures must be higher. Both the pitch and height of the antireflection nanostructures were designed to be 200 nm [7]. The master pattern of antireflection nanostructures was fabricated by electron beam lithography [10].…”

“…Additionally, antireflection function is strongly anticipated for improving a contrast ratio of LCD using frontlight system. For this function, technologies utilizing 100-nm-order nanostructures on the surface of devices have been reported [4,7,8].…”

Manufacturing of highly ordered porous anodic alumina with conical pore shape and tunable interpore distance in the range of 550 nm to 650 nm

“…According to the effective medium theory (EMT), in order to avoid energy loss to diffracted orders, the period of protrusions p must always be smaller than the incident wavelength λ divided by the refractive index of the substrate ns [15,16]. Moreover, the EMT predicts that better light entrapment will occur for larger pillar heights as long as p λ/ns.…”