Degenerate four-wave mixing in triply-resonant Kerr cavities

We demonstrate theoretical conditions for highly-efficient degenerate four-wave mixing in triply-resonant nonlinear (Kerr) cavities. We employ a general and accurate temporal coupled-mode analysis in which the interaction of light in arbitrary microcavities is expressed in terms a set of coupling coefficients that we rigorously derive from the full Maxwell equations. Using the coupled-mode theory, we show that light consisting of an input signal of frequency $\omega_0-\Delta \omega$ can, in the presence of pump light at $\omega_0$, be converted with quantum-limited efficiency into an output shifted signal of frequency $\omega_0 + \Delta \omega$, and we derive expressions for the critical input powers at which this occurs. We find that critical powers in the order of 10mW assuming very conservative cavity parameters (modal volumes $\sim10$ cubic wavelengths and quality factors $\sim1000$. The standard Manley-Rowe efficiency limits are obtained from the solution of the classical coupled-mode equations, although we also derive them from simple photon-counting "quantum" arguments. Finally, using a linear stability analysis, we demonstrate that maximal conversion efficiency can be retained even in the presence of self- and cross-phase modulation effects that generally act to disrupt the resonance condition.Comment: 13 pages, 8 figures. To appear in Physical Review

Delay-bandwidth and delay-loss limitations for cloaking of large objects

Based on a simple model of ground-plane cloaking, we argue that the diffculty of cloaking is fundamentally limited by delay-loss and delaylbandwidth/size limitations that worsen as the size of the object to be cloaked increases relative to the wavelength. These considerations must be taken into account when scaling experimental cloaking demonstrations from wavelength-scale objects towards larger sizes, and suggest quantitative material/loss challenges in cloaking human-scale objects.Comment: 4 pages, 2 figure

Revisión de la validez de constructo del cuestionario de “Características de los profesores de enseñanza del Inglés como lengua extranjera (EFL) exitosos”

The present study re-evaluated the construct validity and reliability of the ‘Characteristics of Successful EFL Teachers’ questionnaire. A total of 814 EFL learners participated in the study. The data were analysed, using exploratory factor analyses (EFA), confirmatory factor analyses (CFA), and reliability analyses. The findings demonstrated all items were loaded on the factors with the relevant content except for two which were loaded on three factors with almost similar loadings. Consequently, they were omitted. Accordingly, factor analysis resulted in seven main factors with 45 items. CFA findings verified the obtained factorial structure. Reliability analyses also provided satisfactory results.El presente estudio reevalúa la validez de constructo y la fiabilidad del cuestionario ‘Características de los profesores de enseñanza del Inglés como lengua extranjera (EFL) exitosos’. En el estudio participaron 814 sujetos. Los datos fueron analizados utilizando análisis factorial exploratorio (EFA) y confirmatorios (CFA). Los resultados mostraron que todos los ítems presentaron saturaciones más altas en los factores a los que pertenecían excepto en dos que presentaron saturaciones similares en tres factores simultáneamente, por lo que fueron suprimidos. El análisis factorial presenta, por tanto siete factores entre los que se distribuyen 45 ítems. Los resultados del análisis factorial confirmatorio se ajusta a esta estructura factorial. El estudio de la fiabilidad llevado a cabo ofrece resultados satisfactorios

Quantum-limited estimation of the axial separation of two incoherent point sources

Improving axial resolution is crucial for three-dimensional optical imaging systems. Here we present a scheme of axial superresolution for two incoherent point sources based on spatial mode demultiplexing. A radial mode sorter is used to losslessly decompose the optical fields into a radial mode basis set to extract the phase information associated with the axial positions of the point sources. We show theoretically and experimentally that, in the limit of a zero axial separation, our scheme allows for reaching the quantum Cram\'er-Rao lower bound and thus can be considered as one of the optimal measurement methods. Unlike other superresolution schemes, this scheme does not require neither activation of fluorophores nor sophisticated stabilization control. Moreover, it is applicable to the localization of a single point source in the axial direction. Our demonstration can be useful to a variety of applications such as far-field fluorescence microscopy.Comment: Comments are welcom

Evaluation of the 40 Hours per Month Work Requirement for MassHealth’s CommonHealth Working Program

Summary: This report evaluates the effectiveness of the 40 hours per month work requirement for eligibility for CommonHealth Working, Massachusetts\u27 Medicaid Buy-In program. The evaluation compared CommonHealth Working to other Massachusetts Medicaid programs and to other state Buy-In programs, examining enrollee earnings, hours worked, expenditures and enrollment patterns. The study also analyzed the impact of eligibility rules and case closure data on enrollment. Prepared for the Commonwealth of Massachusetts Executive Office of Health and Human Services

Deterministically Computing Reduction Numbers of Polynomial Ideals

We discuss the problem of determining reduction number of a polynomial ideal I in n variables. We present two algorithms based on parametric computations. The first one determines the absolute reduction number of I and requires computation in a polynomial ring with (n-dim(I))dim(I) parameters and n-dim(I) variables. The second one computes via a Grobner system the set of all reduction numbers of the ideal I and thus in particular also its big reduction number. However,it requires computations in a ring with n.dim(I) parameters and n variables.Comment: This new version replaces the earlier version arXiv:1404.1721 and it has been accepted for publication in the proceedings of CASC 2014, Warsaw, Polna

The Construct Validity and Reliability of the ‘Characteristics of Successful EFL Teachers Questionnaire (CoSEFLT-Q)’ Revisited

El presente estudio reevalúa la validez de constructo y la fiabilidad del cuestionario ‘Características de los profesores de enseñanza del Inglés como lengua extranjera (EFL) exitosos’. En el estudio participaron 814 sujetos. Los datos fueron analizados utilizando análisis factorial exploratorio (EFA) y confirmatorios (CFA). Los resultados mostraron que todos los ítems presentaron saturaciones más altas en los factores a los que pertenecían excepto en dos que presentaron saturaciones similares en tres factores simultáneamente, por lo que fueron suprimidos. El análisis factorial presenta, por tanto siete factores entre los que se distribuyen 45 ítems. Los resultados del análisis factorial confirmatorio se ajusta a esta estructura factorial. El estudio de la fiabilidad llevado a cabo ofrece resultados satisfactorios.The present study re-evaluated the construct validity and reliability of the ‘Characteristics of Successful EFL Teachers’ questionnaire. A total of 814 EFL learners par-ticipated in the study. The data were analysed, using exploratory factor analyses (EFA), confirmatory factor analyses (CFA), and reliability analyses. The findings demonstrated all items were loaded on the factors with the relevant content except for two which were loaded on three factors with almost similar loadings. Consequently, they were omitted. Accordingly, factor analysis resulted in seven main factors with 45 items.CFA findings verified the ob-tained factorial structure. Reliability analyses also provided satisfactory results