Search results for "Transparency"
showing 10 items of 291 documents
Electromagnetically induced transparency in Doppler-broadened three-level systems with resonant standing-wave drive
2000
We study electromagnetically induced transparency for a probe travelling-wave (TW) laser field in closed Doppler-broadened three-level systems driven by a resonant standing-wave (SW) laser field of moderate intensity (its Rabi frequencies are smaller than the Doppler width of the driven transition). We show that probe windows of transparency occur only for values of the probe-to-drive field frequency ratio R close to half-integer values. For optical transitions and typical values of Doppler broadening for atoms in a vapor cell, we show that for R > 1 a SW drive field is appreciably more efficient than a TW driving in inducing probe transparency. As an example, we consider parameters for a r…
Slowdown and speedup of light pulses using the self-compensating photorefractive response
2011
We study theoretically the effects of pulse slowdown and speedup in ferroelectric Sn2P2S6 possessing a self-compensating photorefractive response. It is shown that both these effects can be implemented in one sample for sufficiently large values of the coupling strength. In contrast to other types of the photorefractive response (local and nonlocal), the output pulses do not suffer from strong spatial amplification and broadening.
Electromagnetically induced transparency with standing-wave drive in the frequency up-conversion regime
2003
We study Electromagnetically Induced Transparency in Doppler-broadened three-level media for probe to drive field frequency ratio R<1 and moderate drive intensities. We show that in this regime a standing-wave drive is more efficient than a travelling-wave one, specially when R is close to half integer values.
Atomic Coherence Effects in Doppler-Broadened Three-Level Systems with Standing-Wave Drive
2001
We study atomic coherence effects (e.g., electromagnetically induced transparency, EIT, and amplification without inversion, AWI) for a probe travelling-wave (TW) laser field in closed Doppler-broadened three-level systems driven by a standingwave (SW) laser field of moderate intensity (its Rabi frequencies are smaller than the Doppler width of the driven transition). We show that probe windows of transparency occur only for values of the probe to drive field frequency ratio R close to half integer values. For optical transitions and typical values of Doppler broadening for atoms in a vapor cell, we show that for R > 1 a SW drive field is appreciably more efficient than a TW drive in induci…
Free-space delay lines and resonances with ultraslow pulsed Bessel beams
2008
We investigate the ultraslow motion of polychromatic Bessel beams in unbounded, nondispersive media. Control over the group velocity is exercised by means of the angular dispersion of pulsed Bessel beams of invariant transverse spatial frequency, which spontaneously emerge from near-field generators. Temporal dynamics in transients and resonances over homogeneous delay lines (dielectric slabs) are also examined.
University Management with Focus on Multicriteria Performance Evaluation: Illustration in the Brazilian Context
2015
Public universities have been facing situations that impel them to improvements in its management towards excellence in reaching, with quality, the objectives for which they were constituted, i.e., to offer teaching, research and extension. In this context, it is up to the managers of the universities to act proactively. The literature points out that the internal control systems are managerial tools capable of providing information for the manager’s actions in his/her activity; however we notice that the academic literature devoted to this demand is still scarce, especially as regards support for decision-making considering organizational specificities. Given the importance of the manager'…
The Design and Execution of Performance Management Systems at State Level: A Comparative Analysis of Italy and Malaysia
2016
ABSTRACTThis comparative study analyses the experience of Italy and Malaysia in the design and execution of performance management systems at the state level. The article investigates how performance management systems have changed over the past decades, the motivations behind their metamorphoses, their common elements across the two countries, and what accounts for the respective progress. It also investigates the role that the institutional framework plays in making performance management systems robust. The study presents policy recommendations on how governments can create more robust performance management systems for enhanced accountability and transparency in an age of resource const…
Criterios relevantes e innovadores del Consejo de Transparencia de la Comunidad Valenciana
2019
espanolLa Comunidad Valenciana ha destacado en los ultimos anos en materia de transparencia. Sin embargo, su Consejo de Transparencia por diversos motivos ha quedado bastante oculto en su intensa labor. El estudio, analiza y expone las resoluciones y criterios mas innovadores y relevantes de este organo en sus cientos de resoluciones habidas desde inicios de 2016. Se considera que muchos de tales criterios deben ser cuanto menos conocidos y, en su caso, incorporarse o, cuanto menos, incitar al debate por especialistas y otros Consejos y autoridades de transparencia estatal o autonomicas. EnglishThe Valencian Community has highlighted in the last years in transparency. However, the intense w…
Acquiescence to opacity
2017
Opacity may affect both the means used to implement policies and the real objectives that they pursue. Our concern with opacity is limited to the cases when it is the result of obfuscation. that is, of some effort on the part of governments or other public bodies (central banks or international organisations) to hide or misrepresent their choices. In the literature concerned with accounting for inefficient policies, there are now models in which opacity plays no significant role. This chapter provides a number of mechanisms that account for or lead to the phenomenon the authors are interested in, that is, voters preferring a policy to be opaque rather than transparent. It then discusses two…
Electromagnetically induced transparency in Doppler-broadened three-level systems with resonant standing wave drive
2005
Summary form only given. Electromagnetically induced transparency (EIT) and related phenomena such as lasing without inversion (LWI) are topics of increasing interest in quantum optics. In EIT, an otherwise absorbing medium is made transparent to a weak coherent field on resonance with a certain atomic transition by applying an intense coherent "driving" field to an adjacent transition. There has been a large number of theoretical papers and EIT was demonstrated experimentally. Up to now, most theoretical papers dealing with EIT in gas media have considered only the case of a traveling (TW) driving field. In contrast, we study EIT in Doppler broadened three-level media with standing wave (S…