Poly nonlinear optics applications

The polysilanes represent another class of polymers that has been extensively studied for nonlinear optical applications [62- ]. These polymers have a molecular structure (R,—Si—R2) that is a long catenated a-bonded silicon backbone with two side groups R, and R2, usually carbon based, attached to each Si atom in the backbone chain. They are soluble in most hydrocarbon solvents and thin films of excellent optical quality can be fabricated with conventional spinning and coating techniques. In spite of the o--bonded nature of the backbone, the poly silanes show extensive electronic delocalization, resulting in strong transitions for excitations polarized parallel to the backbone [65]. They are unique in that they are transparent through the visible to the infrared in contrast to the 7r-electron polymers. 

Nonlinear Optical Applications. Second-order nonlinear (NLO) materials based on ElAPs have shown promise for use in the photonics industry extensive research has been conducted in this area over the past several decades (356,357). Devices based on poly(diacetylene) have been used to demonstrate all-optical switching at 1.6 tm (358). The NLO process occurs when an electromagnetic field interacts with a medium. When the medium is subjected to an electric field E(0) and an optical field E(co), the nonlinear effect arises from field-induced... 

The cadmium chalcogenide semiconductors (qv) have found numerous applications ranging from rectifiers to photoconductive detectors in smoke alarms. Many Cd compounds, eg, sulfide, tungstate, selenide, telluride, and oxide, are used as phosphors in luminescent screens and scintillation counters. Glass colored with cadmium sulfoselenides is used as a color filter in spectroscopy and has recendy attracted attention as a third-order, nonlinear optical switching material (see NONLINEAR OPTICAL MATERIALS). Dialkylcadmium compounds are polymerization catalysts for production of poly (vinyl chloride) (PVC), poly(vinyl acetate) (PVA), and poly(methyl methacrylate) (PMMA). Mixed with TiCl4, they catalyze the polymerization of ethylene and propylene. 

The supramolecular structure of block co-polymers allows the design of useful materials properties such as polarity leading to potential applications as second-order nonlinear optical materials, as well as piezo-, pyro-, and ferroelectricity. It is possible to prepare polar superlattices by mixing (blending) a 1 1 ratio of a polystyrene)-6-poly(butadiene)-6-poly-(tert-butyl methacrylate) triblock copolymer (SBT) and a poly (styrene)-Apoly (tert-butyl methacrylate) diblock copolymer (st). The result is a polar, lamellar material with a domain spacing of about 60 nm, Figure 14.10. 

Conjugated polymers like poly(l,4-phenylene-vinylene), PPV, or more generally Poly(arylene-vinylenes), PAVs have evoked considerable interest as electrically conductive and nonlinear optical materials. More recently, electroluminescence properties of PPV have attracted substantial attention, since it was first reported in 1990. Direct synthesis of PPV has been limited by its insolubility. Hence, the most commonly used routes are based on soluble polymer precursors or soluble conjugated precursors. The latter process is also commonly referred to as the sulfonium-based polyelectrolyte precursor route. PPV thin films from these solution-based routes, however, have problems related to contamination by solvents and oxidative defects in the polymer. C VP is an alternate method for the deposition of high quality thin films of PPV. Reported first by Iwatsuki et al., it was investigated for electroluminescence applications by Staring et al. ... 

Enzymatically synthesized polyphenol derivatives are expected to have great potential for electronic applications. The surface resistivity of poly(p-phe-nylphenol) doped with nitrosylhexafluorophosphate was around 105 Q.4a The iodine-labeled poly(catechol) showed low electrical conductivity in the range from 10 6 to 10 9 S/cm.48 The iodine-doped thin film of poly (phenol- co- tetradecyloxyphenol) showed a conductivity of 10 2 S/cm, which was much larger than that obtained in aqueous 1,4-dioxane.24a The third-order optical nonlinearity (%3) of this film was 10 9 esu. An order of magnitude increase in the third-order nonlinear optical properties was observed in comparison with that prepared in the aqueous organic solution. 

Polymer-embedded gold nanoparticles have been extensively studied [1]. Because of unique physical characteristics, gold-polymer nanocomposites are potentially useful for a number of advanced functional applications, especially in the optical and photonic fields. In particular, these materials can be used as light-stable color filters [2], polarizers [3, 4], ultra-low refractive index materials [5], nonlinear optical devices [6], optical sensors [7], and so on. However, still limited are the chemical routes that allow us to obtain monodispersed thiol-derivatized gold nanoparticles with controlled size to be embedded into poly-... 

Poly(phenylene vinylene) (PPV) is another valuable conjugated polymer, as the synthetic process of PPV is simple and low cost. PPV possesses excellent photoluminescent (PL) and electroluminescent (EL) properties, as well as photovoltaic (PV) and nonlinear optical properties [57]. These properties have led to its being used in broad applications, in such areas as light-emitting diodes (LEDs) and flat-panel displays and photonics applications such as wave-guiding and all-optical switching. 

K-Conjugated polymers and oligomers are organic materials with many interesting and useful properties [1, 2], Examples of this class of materials include polyacetylene, polythiophene, polypyrrole, poly(phenylenevinylene) and their derivatives. Electronic conductivity, luminescence and nonlinear optical behavior are all observed in these materials and these properties have been exploited in applications such as electroluminescent devices (polymer light-emitting devices or PLEDs), electrostatic coatings, electrochromic windows, chemical sensors and memory devices [3-9]. 

Most of the reported conjugated polymers with nonlinear optical or electrical activities are carbon-carbon conjugated systems, such as the extensively studied polyenes (e.g., polyacetylenes [15], polydiacetylenes [16,17], poly-/ -phenylenes) and heteroaromatic polymers (e.g., polypyrroles, polythiophenes, polycarbazoles, polyanilines) [18]. The synthetic methods, applications, and the structure-property relationships of these polymers have also been substantially investigated [19-21]. 

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