Resonant, broadband and highly efficient optical frequency conversion in semiconductor nanowire gratings at visible and UV wavelengths

Using a hydrodynamic approach we examine bulk- and surface-induced second and third harmonic generation from semiconductor nanowire gratings having a resonant nonlinearity in the absorption region. We demonstrate resonant, broadband and highly efficient optical frequency conversion: contrary to conventional wisdom, we show that harmonic generation can take full advantage of resonant nonlinearities in a spectral range where nonlinear optical coefficients are boosted well beyond what is achievable in the transparent, long-wavelength, non-resonant regime. Using femtosecond pulses with approximately 500 MW/cm2 peak power density, we predict third harmonic conversion efficiencies of approximately 1% in a silicon nanowire array, at nearly any desired UV or visible wavelength, including the range of negative dielectric constant. We also predict surface second harmonic conversion efficiencies of order 0.01%, depending on the electronic effective mass, bistable behavior of the signals as a result of a reshaped resonance, and the onset fifth order nonlinear effects. These remarkable findings, arising from the combined effects of nonlinear resonance dispersion, field localization, and phase-locking, could significantly extend the operational spectral bandwidth of silicon photonics, and strongly suggest that neither linear absorption nor skin depth should be motivating factors to exclude either semiconductors or metals from the list of useful or practical nonlinear materials in any spectral range.Comment: 12 pages, 4 figure

Green's function of a finite chain and the discrete Fourier transform

A new expression for the Green's function of a finite one-dimensional lattice with nearest neighbor interaction is derived via discrete Fourier transform. Solution of the Heisenberg spin chain with periodic and open boundary conditions is considered as an example. Comparison to Bethe ansatz clarifies the relation between the two approaches.Comment: preprint of the paper published in Int. J. Modern Physics B Vol. 20, No. 5 (2006) 593-60

Amicable pairs and aliquot cycles for elliptic curves

An amicable pair for an elliptic curve E/Q is a pair of primes (p,q) of good reduction for E satisfying #E(F_p) = q and #E(F_q) = p. In this paper we study elliptic amicable pairs and analogously defined longer elliptic aliquot cycles. We show that there exist elliptic curves with arbitrarily long aliqout cycles, but that CM elliptic curves (with j not 0) have no aliqout cycles of length greater than two. We give conjectural formulas for the frequency of amicable pairs. For CM curves, the derivation of precise conjectural formulas involves a detailed analysis of the values of the Grossencharacter evaluated at a prime ideal P in End(E) having the property that #E(F_P) is prime. This is especially intricate for the family of curves with j = 0.Comment: 53 page

Reevaluation of radiation reaction and consequences for light-matter interactions at the nanoscale

In the context of electromagnetism and nonlinear optical interactions damping is generally introduced as a phenomenological, viscous term that dissipates energy, proportional to the temporal derivative of the polarization. Here, we follow the radiation reaction method presented in [G. W. Ford and R. F. O'Connell, Phys. Lett. A, 157, 217 (1991)], which applies to non-relativistic electrons of finite size, to introduce an explicit reaction force in the Newtonian equation of motion, and derive a hydrodynamic equation that offers new insight on the influence of damping in generic plasmas, metal-based and/or dielectric structures. In these settings, we find new damping-dependent linear and nonlinear source terms that suggest the damping coefficient is proportional to the local charge density, and nonlocal contributions that stem from the spatial derivative of the magnetic field and discuss the conditions that could modify both linear and nonlinear electromagnetic responses.Comment: 11 pages, 1 figure, 19 reference

Reevaluation of radiation reaction and consequences for light-matter interactions at the nanoscale

In the context of electromagnetism and nonlinear optical interactions damping is generally introduced as a phenomenological, viscous term that dissipates energy, proportional to the temporal derivative of the polarization. Here, we follow the radiation reaction method presented in [G. W. Ford and R. F. O'Connell, Phys. Lett. A, 157, 217 (1991)], which applies to non-relativistic electrons of finite size, to introduce an explicit reaction force in the Newtonian equation of motion, and derive a hydrodynamic equation that offers new insight on the influence of damping in generic plasmas, metal-based and/or dielectric structures. In these settings, we find new damping-dependent linear and nonlinear source terms that suggest the damping coefficient is proportional to the local charge density, and nonlocal contributions that stem from the spatial derivative of the magnetic field and discuss the conditions that could modify both linear and nonlinear electromagnetic responses.Comment: 11 pages, 1 figure, 19 reference

Acute respiratory distress syndrome in children with bilateral postviral pneumonia. Case report

USMF „Nicolae Testemițanu”, Catedra Anesteziologie și Reanimatologie, IMSP SCMC „V. Ignatenco”SDRA reprezintă cea mai severă manifestare dintr-un spectru de răspunsuri apărute la diverse leziuni pulmonare acute. Prezentăm un caz clinic de tratament cu succes al unui copil de 1 an si 6 luni, cu sindromul de detresă respiratorie acută. Ca rezultat pozitiv se conclude ca diagnosticarea cât mai precoce a ARDS, urmată de instituirea unui tratament eficace, măresc șansele de recuperare a bolnavilor.ARDS represents the most rigorous manifestation from large variety of acute pulmonary lesions. We present a case report of success treatment of a 1 year and 6 months child with Acute respiratory detress syndrome. As a positive result we conclude that early diagnostic and treatment in ARDS major the optimistic chances in the recovering of the patients

Респираторный дистресс-синдром взрослого со множеством пульмонарных и экстрапульмонарных осложнений в послеродовом периоде (Клинический случай)

USMF „Nicolae Testemiţanu” Catedra Anesteziologie şi Reanimatologie nr. 2, IMSP Institutul Mamei şi Copilului, IMSP Institutul de Ftiziopneumologie „Chiril Draganiuc”, Clinica Otorinolaringologie, Spitalul Clinic RepublicanSummary. A case of a 36-year old woman with Adult Respiratory Distress Syndrome, which was complicated with pneumomediastinum and cardiogenic shock because of the extrapericardiac air tamponation of the heart. The pneumomediastinum was resolved in 4 days. Cardiogenic shock provoked acute renal failure with oliguria and DIC syndrome, which caused acute pulmonary embolism (on the 11th day of the treatment) and neurological aggravation up to coma I. Acute pulmonary embolism changed for the worse pre-existent acute respiratory failure, and the oxygen requirement increased to maximum. An exogenous pulmonary surfactant administration (on the 16-th day of the treatment) was the crucial decision in the management of acute respiratory failure at the discussed patient because after that the oxygen requirement has considerably decreased. On the 20-th day of treatment, oliguria has passed in polyuria, which lasted 9 days. In 7 days after the diuresis normalization, paroxysmal sinus tachycardia with a heart rate of 200 was observed and successfully stopped. Neurological status was nearly completely normalized, but swallowing infringement was observed till the 42 days of treatment. After 58 days of treatment, the patient was sent home.Клинический случай респираторного дистресс-синдрома взрослого, осложненный пневмомедиастинумом и, как следствие, кардиогенным шоком. Пневмомедиастинум разрешился через 4 дня. Кардиогенный шок спровоцировал острую почечную недостаточность и ДВС-синдром, которые в свою очередь явились причиной тромбоэмболии легочной артерии (на 11-й день лечения) и комы. Тромбоэмболия легочной артерии катастрофически ухудшила сердечную недостаточность, потребность в кислороде максимально возросла. Введение экзогенного сурфактанта (на 16-й день лечения) стало поворотным моментом в лечении острой дыхательной недостаточности, после которого потребность в кислороде значительно снизилась. На 20-й день лечения фаза олигурии острой почечной недостаточности сменилась фазой полиурии, которая продлилась 9 дней. На 7-ой день после восстановления адекватного диуреза был зарегистрирован пароксизм синусовой тахикардии (до 200 ударов/минуту), который был с успехом купирован. Неврологический статус пациентки почти полностью нормализовался. До 42 дня лечения наблюдались нарушения глотания вследствие ишемического инсульта. Через 52 лечения пациентка была выписана домой

Luminescence Properties of a Fibonacci Photonic Quasicrystal

We report the realization of an active one-dimensional Fibonacci photonic quasi-crystal via spin coating. Manipulation of the luminescence properties of an organic dye embedded in the quasi-crystal is presented and compared to theoretical simulations. The luminescence occurs via the pseudo-bandedge mode and follows the dispersion properties of the Fibonacci crystal. Time resolved luminescence measurement of the active structure shows faster spontaneous emission rate, indicating the effect of the large photon densities available at the bandedge due to the presence of critically localized states. The experimental results are in excellent agreement with the theoretical calculations.Comment: PDF file, 14 pages 4 figure

Ordered arrays of multiferroic epitaxial nanostructures

Epitaxial heterostructures combining ferroelectric (FE) and ferromagnetic (FiM) oxides are a possible route to explore coupling mechanisms between the two independent order parameters, polarization and magnetization of the component phases. We report on the fabrication and properties of arrays of hybrid epitaxial nanostructures of FiM NiFe2O4 (NFO) and FE PbZr0.52Ti0.48O3 or PbZr0.2Ti0.8O3, with large range order and lateral dimensions from 200 nm to 1 micron