Optically controlled resonance energy transfer:Mechanism and configuration for all-optical switching

In a molecular system of energy donors and acceptors, resonance energy transfer is the primary mechanism by means of which electronic energy is redistributed between molecules, following the excitation of a donor. Given a suitable geometric configuration it is possible to completely inhibit this energy transfer in such a way that it can only be activated by application of an off-resonant laser beam: this is the principle of optically controlled resonance energy transfer, the basis for an all-optical switch. This paper begins with an investigation of optically controlled energy transfer between a single donor and acceptor molecule, identifying the symmetry and structural constraints and analyzing in detail the dependence on molecular energy level positioning. Spatially correlated donor and acceptor arrays with linear, square, and hexagonally structured arrangements are then assessed as potential configurations for all-optical switching. Built on quantum electrodynamical principles the concept of transfer fidelity, a parameter quantifying the efficiency of energy transportation, is introduced and defined. Results are explored by employing numerical simulations and graphical analysis. Finally, a discussion focuses on the advantages of such energy transfer based processes over all-optical switching of other proposed forms. © 2008 American Institute of Physics

All-optical control of molecular fluorescence

We present a quantum electrodynamical procedure to demonstrate the all-optical control of molecular fluorescence. The effect is achieved on passage of an off-resonant laser beam through an optically activated system; the presence of a surface is not required. Following the derivation and analysis of the all-optical control mechanism, calculations are given to quantify the significant modification of spontaneous fluorescent emission with input laser irradiance. Specific results are given for molecules whose electronic spectra are dominated by transitions between three electronic levels, and suitable laser experimental methods are proposed. It is also shown that the phenomenon is sensitive to the handedness of circularly polarized throughput, producing a conferred form of optical activity

Recent Developments in Trade Between the U.S. and the P.R.C.: A Legal and Economic Perspective

This paper presents the life story of a single small-business owner of immigrant background who wants his companyto grow. His business strategies are analysed both as a part of his own biographical work, and as they wereinfluenced and framed by broader political, economic and social processes. It is shown how his own personalqualities in combination with opportunity structures in the local market provided favourable conditions for hisbreak-in. Breaking out, however, seems to be presented with different types of barriers, such as lack of access tocapital, discrimination, and the fact that new markets may consist of different sorts of network that are in its turnmore difficult for new actors to enter. But even if newcomers often find these barriers difficult for to overcome,individuals are not just passive objects but also have the opportunity to realize their lives according to their own lifeplans