Subwavelength structured surfaces: Theory and applications

Detailed theoretical analysis of subwavelength structured (SWS) surfaces is presented. These surfaces are designed for applications in both the visible and infrared portions of the spectrum. Applications presented include antireflection structured (ARS) surfaces, polarization components, narrow-band filters, and phase plates. Experimental results for 2-D binary ARS surfaces are illustrated.; Analysis of SWS surfaces is performed using rigorous coupled-wave analysis (RCWA) and effective medium theory (EMT). EMT is used to derive intuitive analytical formulae that describe a surface's reflection and transmission characteristics. It is shown, by comparing zeroth-order and higher-order EMT, that as the grating period increases, or the substrate index of refraction increases past a certain threshold, zeroth-order EMT results are erroneous and that results derived from higher-order EMT must be used. Comparisons between EMT and RCWA results are made. EMT results, particularly those derived using second-order EMT, are shown to match RCWA. The match between EMT and RCWA is best when the electric field is perpendicular to the grating vector.; ARS surfaces with binary and multi-level 1-D and 2-D profiles are analyzed. The 1-D profiles are shown to be form birefringent and thus better suited for applications involving linearly-polarized light. 2-D profiles are shown to exhibit near-isotropic behavior, and thus are advantageous when randomly polarized radiation is an issue. As the number of levels the profiles contain increases, the tolerance of both 1-D and 2-D structures to bias angles, wavelength detunings, and errors in etch depth increases.; ARS surfaces with 1-D continuous profiles are investigated. Analysis is performed using RCWA, as well as using a novel EMT approach which incorporates tapered transmission-line theory to obtain closed-form solutions for the reflection coefficients. Performance analysis is presented versus grating depth, incident wavelength, and angle of incidence, for the specific cases of triangular and sinusoidal profiles.; As polarization components, SWS surfaces as wire-grid polarizers and wave plates are illustrated. Examples are given for ZnSe quarter-wave plates designed with binary and continuous 1-D profiles. SWS wave plates with continuous profiles have increased throughput due to reflection losses being minimized. For narrow-band filter designs, EMT is used to predict the location of a SWS filter's operating wavelength. As phase plates, the novel use of SWS surfaces to compress laser pulses is presented.; Experimental results are presented for 2-D binary ARS surfaces. These gratings are designed for operation at CO{dollar}sb2{dollar}-laser wavelengths.