Fundamental Limitations to the Ultimate Kerr Nonlinear Performance of Plasmonic Waveguides

Plasmonic waveguides can greatly enhance nonlinear light–matter interactions through strong field confinement. However, achieving high performance nonlinear plasmonic devices remains challenging because of optical losses and material damage. Here we investigate the ultimate Kerr nonlinear performance of plasmonic waveguides. We account for optical damage by requiring that the local electric field intensity does not exceed the damage threshold of the nonlinear material. This allows us to factorize the fundamental limitations into those stemming from the constituent materials’ linear and nonlinear properties, and from the mode characteristics. We define quality coefficients for the metal and for the nonlinear dielectric so that these materials can be selected appropriately, and illustrate their utility by application to surface plasmon polaritons (SPPs). We further propose the concept of nonlinear effectiveness in order to quantify a mode’s ability to exploit the material’s nonlinearity. We find that the full exploitation of the material’s maximum nonlinearity requires a uniform field in addition to slow light effects. This is exemplified by the discovery that the maximum nonlinearity of Metal–Dielectric–Metal structures can be stronger than that of the bulk material. These counterintuitive insights provide deep understanding into the ultimate performance of nonlinear waveguides, and point to novel approaches to achieve practical, high performance nonlinear plasmonic devices

Fundamental Limitations to the Ultimate Kerr Nonlinear Performance of Plasmonic Waveguides

Plasmonic waveguides can greatly enhance nonlinear light–matter interactions through strong field confinement. However, achieving high performance nonlinear plasmonic devices remains challenging because of optical losses and material damage. Here we investigate the ultimate Kerr nonlinear performance of plasmonic waveguides. We account for optical damage by requiring that the local electric field intensity does not exceed the damage threshold of the nonlinear material. This allows us to factorize the fundamental limitations into those stemming from the constituent materials’ linear and nonlinear properties, and from the mode characteristics. We define quality coefficients for the metal and for the nonlinear dielectric so that these materials can be selected appropriately, and illustrate their utility by application to surface plasmon polaritons (SPPs). We further propose the concept of nonlinear effectiveness in order to quantify a mode’s ability to exploit the material’s nonlinearity. We find that the full exploitation of the material’s maximum nonlinearity requires a uniform field in addition to slow light effects. This is exemplified by the discovery that the maximum nonlinearity of Metal–Dielectric–Metal structures can be stronger than that of the bulk material. These counterintuitive insights provide deep understanding into the ultimate performance of nonlinear waveguides, and point to novel approaches to achieve practical, high performance nonlinear plasmonic devices

Supplementary document for Rational design of an integrated directional coupler for wideband operation - 6756461.pdf

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Reference intervals for hemoglobin and hematocrit in a low-risk pregnancy cohort: implications of racial differences

<p><b>Objective:</b> As anemia in pregnancy is associated with adverse perinatal outcomes, we sought to define the mean and the fifth percentile of Hb and Ht using a contemporary multiethnic large cohort of low-risk pregnancies, and assess potential racial differences.</p> <p><b>Methods:</b> We conducted a retrospective cohort study on women who delivered between 1 January 2008 and 31 December 2013 in Reggio Emilia County, Italy. Linear mixed effects models were used to describe changes in mean Hb and Ht, while quantile regression with matrix-design bootstrap defined changes in the fifth percentile of Hb and Ht, controlling for race, maternal age, smoking, and pregnancy number.</p> <p><b>Results:</b> We analyzed 23,657 hemograms from 7318 pregnancies and 6870 women. Multivariate analysis showed that when compared to Caucasians’, African women’s mean Hb and Ht were respectively 0.24 (95%CI 0.3–0.17) g/dl and 0.7 (95%CI 0.8–0.5) % lower, while Asian mothers’ were 0.11 (95%CI 0.19–0.03) g/dl and 0.3 (95%CI 0.5–0.1) % inferior. Similarly, both African and Asian women had lower fifth Ht percentiles (−1, 95%CI −1.3 to −0.6, and −0.4, 95%CI −0.7 to −0.04) than Caucasians, while African mothers also had lower fifth Hb percentile (0.3, 95%CI 0.5–0.1). The fifth percentile for Hb and Ht were, respectively, 11.3 (95%CI 11–11.5) g/dl and 32.8 (95%CI 32.3–33.4) % in the first trimester, 10.4 (95%CI 10.1–10.6) g/dl and 30.2 (95%CI 29.6–30.8) % in the second trimester, 10.1 (95%CI 9.8–10.3) g/dl and 30.6 (95%CI 30–31.1) % in the third trimester.</p> <p><b>Conclusions:</b> We provided contemporary references to define anemia in pregnancy, and we confirmed that even in pregnancy, African and Asian women have lower Hb and Ht than Caucasian. Racial and population-specific references may have significant clinical and public health implication for more accurate disease diagnosis and appropriate treatment.</p

Supplement 1: Midinfrared supercontinuum generation from 2 to 6 μm in a silicon nanowire

Supplemental document Originally published in Optica on 20 September 2015 (optica-2-9-797