Effect of wavelength dependence of nonlinearity, gain, and dispersion in photonic crystal fiber amplifiers

Photonic crystal fibers are used in fiber amplifiers and lasers because of the flexibility in the design of mode area and dispersion. However, these quantities depend strongly on the wavelength. The wavelength dependence of gain, nonlinearity and dispersion are investigated here by including the wavelength dependence explicitly in the nonlinear Schr\"odinger equation for photonic crystal fibers with varying periods and hole sizes. The effect of the wavelength dependence of each parameter is studied separately as well as combined. The wavelength dependence of the parameters is shown to create asymmetry to the spectrum and chirp, but to have a moderating effect on pulse broadening. The effect of including the wavelength dependence of nonlinearity in the simulations is demonstrated to be the most significant compared that of dispersion or gain

Conditions for waveguide decoupling in square-lattice photonic crystals

We study coupling and decoupling of parallel waveguides in two-dimensional square-lattice photonic crystals. We show that the waveguide coupling is prohibited at some wavelengths when there is an odd number of rows between the waveguides. In contrast, decoupling does not take place when there is even number of rows between the waveguides. Decoupling can be used to avoid cross talk between adjacent waveguides.Comment: 6 pages, 2 figure

Transport model for hot positrons in layered structures

The transport of hyperthermal, monoenergetic (≤10-eV) positrons injected in metal bilayer structures is investigated. The transport is modeled using the Boltzmann equation and the two-flux approximation. Analyzing reported experimental data in terms of the developed model enables us to separate the different scattering channels and to estimate the mean free paths for these events. Our study is the first quantitative treatment of hot positrons, and the extracted transport parameters agree with theoretical predictions.Peer reviewe

Prediction of Early Childhood Negative Emotionality and Inhibition From Maternal Distress During Pregnancy

The association was investigated between psychological distress reported during each trimester of pregnancy and maternal ratings of temperament when the children were 6 months and 5 years of age. Mothers in the greater Helsinki area who were to give birth during a 1-year period completed a brief questionnaire describing their psychological adjustment and medical symptoms at each prenatal visit to government health clinics. Mothers rated their children\u27s temperament at ages 6 months and 5 years. Maternal psychological distress during pregnancy was only modestly associated with infant temperament. However, maternal distress during the first trimester was associated with ratings of negative emotionality at age 5 years, with a stronger correlation for males. Inhibition at age 5 was predicted by infant distress to novelty, particularly for males

Long-term clinical and economic outcomes in previously untreated paediatric patients with severe haemophilia A : A nationwide real-world study with 700 person-years

AimFor previously untreated patients (PUPs) with severe haemophilia A in Finland for the past 2 decades, the standard practice has been to start early primary prophylaxis. We evaluated the long-term clinical outcomes and costs of treatment with high-dose prophylaxis in PUPs from birth to adolescence, including immune tolerance induction (ITI). MethodsFrom the medical records of all PUPs born between June 1994 and May 2013 in Finland, we retrospectively extracted data on clinical outcomes and healthcare use. Using linear mixed models, we analysed longitudinal clinical outcome data. To analyse skewed cost data, including zero costs, we applied hurdle regression. ResultsAll 62 patients received early regular prophylaxis; totally, they have had treatment for nearly 700 patient-years. The median age of starting home treatment was 1.1years. The mean (SD) annual treatment costs (Europerkg) were 4391Euro (3852). For ages 1-3, ITI comprised over half of the costs; in other groups, prophylactic FVIII treatment dominated. With these high costs, however, clinical outcomes were desirable; median (IQR) ABR was low at 0.19 (0.07-0.46) and so was AJBR at 0.06 (0-0.24). Thirteen (21%) patients developed a clinically significant inhibitor, 10 (16%) with a high titre. All ITIs were successful. The mean costs for ITI were 383448Euro (259085). The expected ITI payback period was 1.81 (95% CI 0.62-12.12) years. ConclusionsEarly high-dose prophylaxis leads to excellent long-term clinical outcomes, and early childhood ITI therapy seems to turn cost-neutral generally already in 2years.Peer reviewe

Guiding and reflecting light by boundary material

We study effects of finite height and surrounding material on photonic crystal slabs of one- and two-dimensional photonic crystals with a pseudo-spectral method and finite difference time domain simulation methods. The band gap is shown to be strongly modified by the boundary material. As an application we suggest reflection and guiding of light by patterning the material on top/below the slab.Comment: 12 pages, 7 figure