1,721,004 research outputs found
Angle-resonant stimulated polariton amplifier
Full text linkWe experimentally demonstrate resonant coupling between photons and excitons in microcavities which can efficiently generate enormous single-pass optical gains approaching 100. This new parametric phenomenon appears as a sharp angular resonance of the incoming pump beam, at which the moving excitonic polaritons undergo very large changes in momentum. Ultrafast stimulated scattering is clearly identified from the exponential dependence on pump intensity. This device utilizes boson amplification
induced by stimulated energy relaxation
Stimulated spin dynamics of polaritons in semiconductor microcavities
Full text linkTime-resolved polarization spectroscopy of polariton pair scattering in semiconductor microcavities enables complete measurement of the polariton spin dynamics. In addition to spin-preserving interactions previously reported, we observe two additional even stronger scattering processes, which mix polaritons of opposite spin. Because of the polaritons' bosonic character, this results in the stimulation of spin flips. Such mechanisms should allow realization of spin-sensitive interferometers
Off-branch polaritons and multiple scattering in semiconductor microcavities
No full textAngle-resolved measurements show unexpected emission resonances of the polaritons in a semiconductor microcavity. These resonances appear when more than one in-plane polariton mode is macroscopically occupied. The new resonances observed in angle-resolved luminescence do not lie on the expected polariton branches and possess different dispersion relations with negative effective mass. The experimental results can be well explained using an interacting polariton model that treats multiple scattering. The k dispersion of the luminescence resonances is reproduced using the Bogolubov approximation that deals with the macroscopic coherence of the signal, pump, and idler modes. This model also explains many puzzling features such as the stimulation of resonant Rayleigh scattering in the backward direction. In addition, the use of nonresonant control beams for coherent control of the polaritons is shown both experimentally and theoretically. The rich complexity of new phenomena in optically excited semiconductor microcavities can be attributed to the distinctive anti-Hermitian or anomalous coupling between polaritons
Asymmetric angular emission in semiconductor microcavities
Full text linkStrongly angular-dependent emission properties are observed from a semiconductor microcavity pumped
along a critical angle of incidence. In contrast to the luminescence from conventional semiconductor heterostructures,the emission is completely asymmetrical with respect to the sample normal. The results imply that
parametric scattering dominates the energy relaxation of polaritons, and is enhanced by the deformed shape of
the dispersion relations
Confined Plasmons in Metallic Nanocavities
No full textWe investigate the properties of gold surfaces patterned using a nanoscale "lost wax" technique by electrochemical deposition through a self-assembled latex template. Near-spherical gold nanocavities within the resulting porous films support localized surface plasmons which couple strongly to incident light, appearing as sharp spectral features in reflectivity measurements. The energy of the resonances is easily tunable from ultraviolet to near infrared by controlling the diameter and height of the nanocavities. The energies of these features agree well with the Mie resonances of a perfect spherical void
Optical trirefringence in photonic crystal waveguides
No full textWe demonstrate that 2D photonic crystals can possess optical trirefringence in which there are six field orientations for which linear incident light is not perturbed on reflection or transmission. Such a property is rigorously forbidden in homogeneous nonmagnetic dielectrics which can possess only optical birefringence. We experimentally demonstrate this phenomena in silicon-based mesostructures formed from photonic crystal waveguides embedded in a Fabry-Perot cavity. Multirefringence is controlled by the presence of submicron dielectric patterning and is well explained by an exact scattering matrix theory
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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