Doping nonlinear materials

For devices the important classes of nonlinear materials are (i) molecular and polymeric materials, (ii) multiple quantum well semi-conductors, (hi) bulk semiconductors and (iv) semiconductor doped glasses. Of these classes, organic polymeric structures have shown the largest non-resonant x - Important nonlinearities observed in inorganic semiconductor materials are in a narrow wavelength region determined by excitonic resonances. Therefore, these nonlinearities are resonant, slower in response and produce thermal effects. 

Systems in which acetylenic spacers are placed between the pyridine and the thiophene rings have been reported (LVI). In these cases, the thiophene ring contained 3-hexyl or 3,4-dinitro groups [54]. These polymers can be electrochemical y n-doped more easily than they can be p-doped. These materials are also of interest because of their large third-order nonlinear optical properties. 

Polymethyl(methacrylate) doped with 4-substituted 3-arylsydnones provide a promising class of nonlinear optical materials with various potential applications <2007SM142>. 

The results of the above analysis suggest that the formation of macro PS on lowly doped materials can be associated with a nonlinear potential distribution in the solid of a curved surface due to the high resistivity of the solid. The formation of two-layer PS on... 

When the resistance of the substrate is high and a significant amount of potential is dropped in the substrate, the potential drop may not be uniform along a curved pore bottom due to the nonlinear potential distribution on the material surrounding the bottom. Formation of macro PS on lowly doped materials becomes possible under such a condition. 

Polysilanes are cr-conjugated polymers composed of Si-Si skeletons and organic pendant groups. They are insulators with filled intramolecular valence bands and empty intramolecular conduction bands. However, because of strong cr conjugation, they have rather narrow band gaps of less than 4 eV [24,25] and are converted to conductors by photoexcitation or by doping electron donors or acceptors. Recently they have attracted much attention because of their potential utility as one-dimensional conductors, nonlinear optical materials, and electroluminescent materials [26-28]. 

Monodisperse spherical colloids and most of the applications derived from these materials are still in an early stage of technical development. Many issues still need to be addressed before these materials can reach their potential in industrial applications. For example, the diversity of materials must be greatly expanded to include every major class of functional materials. At the moment, only silica and a few organic polymers (e.g., polystyrene and polymethylmethacrylate) can be prepared as truly monodispersed spherical colloids. These materials, unfortunately, do not exhibit any particularly interesting optical, nonlinear optical or electro-optical functionality. In this regard, it is necessary to develop new methods to either dope currently existing spherical colloids with functional components or to directly deal with the synthesis of other functional materials. Second, formation of complex crystal structures other than closely packed lattices has been met with limited success. As a major limitation to the self-assembly procedures described in this chapter, all of them seem to lack the ability to form 3D lattices with arbitrary structures. Recent demonstrations based on optical trapping method may provide a potential solution to this problem, albeit this approach seems to be too slow to be useful in practice.181-184 Third, the density of defects in the crystalline lattices of spherical colloids must be well-characterized and kept below... 

Typical values of the second-order nonlinear coefficient d for dielectric crystals, semiconductors, and organic materials used in photonics applications lie in the range d = 10 24 to 10 - (mks units, As/V2). Typical values of the third-order nonlinear coefficient x(3> for glasses, crystals, semiconductors, semiconductor-doped glasses, and organic materials of interest in photonics are x -3 = 10 34 to 10 29 (mks units). 

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