Biomedical subjects

R P Stanley

Publications and source records attributed to R P Stanley.

3 recordsLinked to original sources

PubMed2001

Parametric polariton amplification in semiconductor microcavities.

We present novel experimental results demonstrating the coherence properties of the nonlinear emission from semiconductor microcavities in the strong coupling regime, recently interpreted by parametric polariton four-wave mixing. We use a geometry corresponding to degenerate four-wave mixing. In addition to the predicted threshold dependence of the emission on the pump power and spectral blueshift, we observe a phase dependence of the amplification which is a signature of a coherent polariton wave mixing process.

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PubMed2001

Coupling of impurity modes in one-dimensional periodic systems.

One-dimensional periodic dielectric structures are known to exhibit band gaps because of their symmetry. Defect states can be found in the band gaps if an impurity layer is added to the lattice such that the symmetry of the structure is broken. In this paper, we consider the case where a second impurity layer is added and we discuss the existence of coupling between the two defects. We discuss the possibility of exploiting the coupling of impurity modes in the realization of tunable wavelength emitting devices and dual-wavelength vertical-cavity surface-emitting lasers.

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PubMed1996

Hyperplane arrangements, interval orders, and trees.

A hyperplane arrangement is a finite set of hyperplanes in a real affine space. An especially important arrangement is the braid arrangement, which is the set of all hyperplanes xi - xj = 1, 1 </= i < j </= n, in Rn. Some combinatorial properties of certain deformations of the braid arrangement are surveyed. In particular, there are unexpected connections with the theory of interval orders and with the enumeration of trees. For instance, the number of labeled interval orders that can be obtained from n intervals I1,..., In of generic lengths is counted. There is also discussed an arrangement due to N. Linial whose number of regions is the number of alternating (or intransitive) trees, as defined by Gelfand, Graev, and Postnikov [Gelfand, I. M., Graev, M. I., and Postnikov, A. (1995), preprint]. Finally, a refinement is given, related to counting labeled trees by number of inversions, of a result of Shi [Shi, J.-Y. (1986), Lecture Notes in Mathematics, no. 1179, Springer-Verlag] that a certain deformation of the braid arrangement has (n + 1)n-1 regions.

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