Quantum optics future applications

While the linear absorption and nonlinear optical properties of certain dendrimer nanocomposites have evolved substantially and show strong potential for future applications, the physical processes governing the emission properties in these systems is a subject of recent high interest. It is still not completely understood how emission in metal nanocomposites originates and how this relates to their (CW) optical spectra. As stated above, the emission properties in bulk metals are very weak. However, there are some processes associated with a small particle size (such as local field enhancement [108], surface effects [29], quantum confinement [109]) which could lead in general to the enhancement of the fluorescence efficiency as compared to bulk metal and make the fluorescence signal well detectable [110, 111]. 

The work described in this paper is an illustration of the potential to be derived from the availability of supercomputers for research in chemistry. The domain of application is the area of new materials which are expected to play a critical role in the future development of molecular electronic and optical devices for information storage and communication. Theoretical simulations of the type presented here lead to detailed understanding of the electronic structure and properties of these systems, information which at times is hard to extract from experimental data or from more approximate theoretical methods. It is clear that the methods of quantum chemistry have reached a point where they constitute tools of semi-quantitative accuracy and have predictive value. Further developments for quantitative accuracy are needed. They involve the application of methods describing electron correlation effects to large molecular systems. The need for supercomputer power to achieve this goal is even more acute. 

Abstract Silver clusters, composed of only a few silver atoms, have remarkable optical properties based on electronic transitions between quantized energy levels. They have large absorption coefficients and fluorescence quantum yields, in common with conventional fluorescent markers. But importantly, silver clusters have an attractive set of features, including subnanometer size, nontoxicity and photostability, which makes them competitive as fluorescent markers compared with organic dye molecules and semiconductor quantum dots. In this chapter, we review the synthesis and properties of fluorescent silver clusters, and their application as bio-labels and molecular sensors. Silver clusters may have a bright future as luminescent probes for labeling and sensing applications. 

High quantum yield photochemical reactions of condensed-phase species may become useful for future optical applications such as molecular switches, optical limiters, and read-write data storage media. Toward these ends, much research has been conducted on novel nonlinear chemical-based materials such as conducting polymers and metal-organic species. Monitoring the early time-dependent processes of these photochemical reactions is key to understanding the fundamental mechanisms and rates that control the outcome of these reactions, and this could lead to improved speed and efficiencies of devices. 

Some aspects of computational quantum chemistry applied to the analysis of the electronic structure of polymers are reviewed in connection with the timely trends observed in their electrical and optical properties. The paper is organized as follows after an introduction (Section 36.1), the basic theory of the quantum chemical methodologies as applied to periodic chains is summarized (Section 36.2). Several fields of applications are then presented photoelectron spectra (Section 36.3), conducting and semiconducting conjugated polymers (Section 36.4), hnear and non-linear optical properties (Section 36.5) and the role of charge transfer in organic chains (Section 36.6). Possible developments for the near future are also sketched. 

After briefly considering the relevant results pertinent to multiple-quantum direct detection (Sec. 7.2.1), we derive the combination device response for the general multiple-quantum photomixing process (including the important two-quantum case) in Section 7.12. In Section 7.2.3, we obtain the SNR for a receiver using a multiphoton optical heterodyne device, and compare it with the SNR for conventional optical heterodyne detection. The results of a two-photon experiment are presented in Section 7.2.4, while a suggested setup for future experiments, as well as the applicability of the scheme in general, is reserved for Section 7.2.5. 

Many technical challenges remain for the use of nanocomposite materials in future optical applications. These challenges cover the fundamental and experimental aspects of the research in materials, designs, and devices. The progress made in nanomaterials and nanotechnology has been encouraging and has allowed the fabrication and use of new nanostructures such as nanopartides, nanowires, nanorods, quantum dots in numerous new applications. It is expected that the... 

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