Light propagation control by finite-size effects in photonic crystals

We exhibit the strong influence on light propagation of the finite size in photonic band-gap material. We show that light emission can be controlled by the symmetry group of the boundary of the finite device. These results lead simply to important practical applications.Comment: 5 pages, 4 figures, Revte

Alleviating Oral Communication Anxieties in College French Classes: The Impact of Professor-Student Connections

Oral communication anxiety (OCA) is a challenge for many college students studying a foreign language. This phenomenon has yielded many studies explaining OCA exists, relating it to personality traits and concluding educators play a large role in either reducing or aggravating such anxieties. However, research is lacking in the role professor-student rapport and connections play in affecting OCA. Thus, the purpose of this qualitative study was to seek student perception on (through their worldviews), and recommendations for, professor teaching practices as it relates to anxiety and rapport-building. The participants are and were students of French in an undergraduate private liberal arts college in the Midwest region of the United States. Some of the findings referring to teaching practices were expected while other findings were surprising. For example, the very people who should reduce anxiety (professors) were sometimes the ones who aggravated it unknowingly. The recommendations participants shared were also unpredictable, surprising, and unexpected especially as they pertained to professor-student rapport outside of the classroom. Among recommendations were that professors make the academic environment as relaxed and welcoming as possible. Teaching practices, such as focusing on small group or pair activities were valued for their relatively low impact on oral communication anxiety and students recommended professors focus on these types of activities. Rapport building outside of the classroom was not deemed as important to students who experienced oral communication anxieties and no suggestions were made to improve it. The participants were concerned about the rapport inside of the classroom and professor pedagogical approaches

El bicentenario de la Constitución de Cádiz y su proyección en Iberoamérica

[Resumen] La Constitución Política de la Monarquía Española, promulgada en Cádiz el 19 de Marzo de 1812, constituyó uno de los ensayos constitucionales mejor concebidos acerca de la organización del Estado que introdujo, por primera vez en España, un sistema tendiente a proteger los derechos de propiedad y libertad de los ciudadanos. Desde ese punto de partida, se sostiene, en este trabajo, que la Constitución de Cádiz de 1812 representa una síntesis, realmente original, en la que se conjugan una serie de principios provenientes del antiguo derecho español y de la neo-ecolástica salmantina con el liberalismo en boga hacia fines del siglo XVIII, si bien con los matices propios de la tradición hispánica. La culminación de ese proceso implicó el quiebre del régimen absolutista mediante la transformación de las estructuras existentes. La Constitución gaditana reposa, a juicio del autor, en tres ejes centrales, a saber: a) la soberanía nacional; b) la doctrina de la separación de poderes y, consecuentemente la independencia del poder judicial; y, c) el principio de legalidad. Su proyección en Hispanoamérica ha sido notable reflejándose, fundamentalmente, en el sistema judicialista puro que adoptan la mayoría de las constituciones, al consagrar la interdicción del ejercicio de funciones judiciales por parte del Ejecutivo y del Legislativo con un alcance distinto al que rige en la Constitución de los Estados Unidos, donde se admite la constitucionalidad de la jurisdicción administrativa primaria.[Abstract] The Politic Constitution of the Spanish Monarchy promulgated in Cadiz on March 19th 1812 (the Cadiz Constitution) was one of the best constitutional systems ever conceived on organization of the State which introduced, for the first time in Spain, a legal system tending to protect the right of property and the liberty of citizens. From this starting point, the author of this article postulates that the Cadiz Constitution represents a really-original synthesis, where different principles coming from the ancient Spanish law and from the later Spanish Scholastics of Salamanca, combine with other liberal conceptions in vogue toward the end of the 18th century, although acknowledging connotations that befit the Spanish tradition. The culmination of said process meant the breakdown of the absolutist regime by means of existent structures transformation. The Cadiz Constitution leaned, according to the author, on three main premises, thus: (a) on national sovereignty, (b) on separation of powers doctrine (consequently, on independence of the judicial branch); and (c) on rule of law. Its projection on Spanish America has been remarkable, and it becomes self evident in the purely-judicialist system of their constitutions, all of which ban the Executive and Legislative branches from exercising judicial functions, differently from the Constitution of the United States of America, where administrative primary jurisdiction is constitutionally allowed

Efficient light coupling from integrated single-mode waveguides to supercollimating photonic crystals on silicon-on-insulator platforms

We propose a practical and efficient solution for the coupling of light from integrated single-mode waveguides to supercollimating planar photonic crystals on conventional silicon-on-insulator platforms. The device consists of a rib waveguide, designed to sustain spatially extended single-modes and matched to a supercollimating photonic crystal, which has been truncated at its boundary to improve impedance matching between the two photonic components. Three-dimensional simulations show transmission efficiencies up to 96 % and reflections below 0.2 % at wavelengths close to 1.55 microns. This approach constitutes a significant step toward the integration of supercollimating structures on photonic chips.Comment: 11 pages, 4 figure

Spatially resolved phase objects using Mach–Zehnder interferometry

Phase characterization with a good spatial resolution is crucial for focused beams in nonlinear media. The phase-shifting interferometry technique, using the least-squares error criterion for several interferograms, is implemented using a reflective spatial light modulator (SLM). The method provides a convenient calibration for any phase-shift steps. The reliability of the proposed method is checked by direct comparison with results obtained by the Fourier transform method as well as using a previously characterized circular phase object