Midinfrared semiconductor optical metamaterials

We report on a novel class of semiconductor metamaterials that employ a strongly anisotropic dielectric function to achieve negative refraction in the midinfrared region of the spectrum, ~8.5–13 μm. We present two types of metamaterials, layered highly doped/undoped heterostructures and quantum well superlattices that are highly anisotropic. Contrary to other optical metamaterials these heterostructure systems are optically thick (up to 20 μm thick), planar, and require no additional fabrication steps beyond the initial growth. Using transmission and reflection measurements and modeling of the highly doped heterostructures, we demonstrate that these materials exhibit negative refraction. For the highly doped quantum well superlattices, we demonstrate anomalous reflection due to the strong anisotropy of the material but a determination of the sign of refraction is still difficult. This new class of semiconductor metamaterials has great potential for waveguiding and imaging applications in the long-wave infrared

Characterization Of The Macular Choriocapillaris In Dry Age-Related Macular Degeneration Using Swept-Source Optical Coherence Tomography Angiography

The purpose of this study was to characterize further, using swept-source (SS-) optical coherence tomography angiography (OCTA), the relationship between dry age-related macular degeneration (AMD) and the macular choriocapillaris (CC), which may have pathophysiologic and therapeutic implications. It included (1) a topographic analysis to determine if there is a significant relationship between dry AMD stage and macular CC perfusion, and (2) an investigation of the predictive value of macular CC perfusion with respect to geographic atrophy (GA) growth rate. Study design was retrospective and cross-sectional. A database of 6x6 mm fovea-centered swept-source OCTA images of the CC from eyes with early, intermediate, and advanced dry AMD (56 eyes, 41 patients) was generated using automated and manual segmentation. In (1), these images were analyzed using algorithms described in the literature to assess CC perfusion deficit metrics (flow deficit percentage (FD%) and average flow deficit size). Regions were defined by concentric areas centered on the fovea: a 1 mm diameter area, 3 mm diameter ring, 5 mm diameter area, 5 mm diameter ring, and 6x6 mm whole image. Data were modeled using the generalized estimating equations (GEE) approach. In (2), OCTA images from the database having GA as well as corresponding autofluorescence (AF) structural imaging at multiple time points (13 eyes, 10 patients) were analyzed for CC perfusion deficit metrics. These were plotted against the square root transformation of average GA growth rate, determined by AF over periods up to 52 months. Results of (1) showed that the relationship between age and CC FD% and average flow deficit size was statistically significant (p ≤ .05) in all regions of analysis. The relationship between dry AMD stage and FD% was statistically significant in the 5 mm ring, and between dry AMD stage and average flow deficit size in the 3 mm ring, 5 mm area, 5 mm ring, and 6x6 mm whole image. Results of (2) showed a significant positive linear correlation between CC perfusion deficit metrics (flow deficit %: Pearson’s r = .68; average flow deficit size: Pearson’s r = .69) and the square root transformation of average GA growth rate. In conclusion, generation of a unique database of SS-OCTA imaging of the CC in all stages of dry AMD enabled an improved understanding of the relationship between CC perfusion and dry AMD. Specifically, this study found a statistically significant relationship between dry AMD stage and CC perfusion, most prominent in the more peripheral regions of the macula, and suggested that a positive linear correlation between CC perfusion deficit and the square root transformation of average GA growth rate holds over periods up to 52 months

Topographic analysis of macular choriocapillaris flow deficits in diabetic retinopathy using swept–source optical coherence tomography angiography

BACKGROUND: The purpose of this study was to investigate the association between diabetic retinopathy (DR) severity and macular choriocapillaris (CC) flow deficit percentage (FD %) in different macular regions using swept-source optical coherence tomography angiography (SS-OCTA). METHODS: Diabetic patients with SS-OCTA images were graded by severity and retrospectively assessed. CC FD % was calculated in four different regions of the OCTA image: inner, middle, outer, and full-field region. The generalized estimating equations (GEE) approach for clustered eye data was used to determine effect size and significance of age and disease severity on FD % for each region. RESULTS: 160 eyes from 90 total diabetic patients met inclusion criteria. Out of 90 patients, 33 had no DR, 17 had mild nonproliferative DR (NPDR), 8 had moderate NPDR, 10 had severe NPDR and 22 had proliferative DR. Age and DR severity had a significant positive association with FD % for each region studied with a greater effect in the two centermost regions. The increase in flow deficit percentage per year of age by region was: inner 0.12 (p < 0.001), middle 0.09 (p < 0.001), outer 0.05 (p < 0.001, full-field 0.06 (p < 0.001). The increase in flow deficit percentage per increase in diabetic retinopathy severity stage by region was: inner 0.65 (p < 0.0087), middle 0.56 (p < 0.0012), outer 0.33 (p < 0.045), full-field 0.36 (p < 0.018). CONCLUSIONS: Topographic analysis of the CC FD % in diabetic eyes suggests that CC flow impairment corresponds to DR severity, with all studied regions of the CC significantly affected. There was greater regional impairment due to age and disease severity in the inner and middle regions.National Institutes of Health (Grant Number 5-R01-EY011289-31)Air Force Ofce of Scientifc Research (Grant Number FA9550-15-1-0473

Global Analysis of Macular Choriocapillaris Perfusion in Dry Age-Related Macular Degeneration using Swept-Source Optical Coherence Tomography Angiography

PURPOSE: Swept-source optical coherence tomography angiography (SS-OCTA) was used to investigate if the clinical stage of dry age-related macular degeneration (AMD) was correlated with global and regional macular choriocapillaris (CC) perfusion. METHODS: In this retrospective, cross-sectional study, 6 3 6-mm SS-OCTA images from eyes with early, intermediate, and advanced dry AMD (56 eyes, 41 patients) were analyzed using algorithms described in the literature to assess regional flow deficit percentage (FD%) and average flow deficit size. Regions were defined by concentric areas centered on the fovea: a 1-mm-diameter area, 3-mm-diameter ring, 5-mm-diameter area, 5-mm-diameter ring, and 6 3 6-mm whole image. Data were modeled using the generalized estimating equations approach. RESULTS: The relationship between age and CC FD% and average flow deficit size was statistically significant (P ≼ 0.05) in all regions of analysis by linear modeling. The relationship between dry AMD stage and FD% was statistically significant by linear modeling in the 5-mm ring, and between dry AMD stage and average flow deficit size in the 3-mm ring, 5-mm area, 5-mm ring, and 6 3 6-mm whole image. CONCLUSIONS. Linear modeling suggests a statistically significant relationship between dry AMD stage and CC perfusion, most prominent in the more peripheral regions of the macula.National Institutes of Health (Grant 5-R01- EY011289-31)Air Force Office of Scientific Research (Grant FA9550-15-1-0473)National Institute of Diabetes and Digestive and Kidney Diseases Medical Student Research Fellowship (Award T35DK104689)National Center for Advancing Translational Sciences (Award TL1-TR001864

Structure and macroscopic tackiness of ultra-thin pressure sensitive adhesive films

Ultrathin layers of the statistical copolymer P(nBA-stat-MA) with a majority of n-butyl acrylate (nBA) and a minority of methyl acrylate (MA) are characterized with respect to the film morphology and the mechanical response in a probe tack test. The probed copolymer can be regarded as a model system of a pressure sensitive adhesive (PSA). The films are prepared by spin-coating which enables an easy thickness control via the polymer concentration of the solution. The film thickness is determined with x-ray reflectivity (XRR) and white light interferometry (WLI). Grazing incidence small angle x-ray scattering (GISAXS) provides detailed and statistically significant information about the film morphology. Two types of lateral structures are identified and no strong correlation of these structures with the PSA film thickness is observed. In contrast, prominent parameters of the probe tack test, such as the stress maximum and the tack energy, exhibit an exponential dependence on the film thickness