Nonlinear materials polymeric devices

Champagne, B., Kirtman, B. Theoretical approach to the design of organic molecular and polymeric nonlinear optical materials. In Handbook of Advanced Electronic and Photonic Materials and Devices, vol. 9. Academic, San Diego (2001)... 

Fullerene has important properties as a nonlinear material, particularly as an optical limiting material with applications in device fabrication. The poor solubility of this material and the processing difficulties associated with it severely limit its direct application, however. One possibility of overcoming these disadvantages involves binding polymers on to Ceo to obtain fullerene-based polymeric materials with peculiar physical and/or chemical properties and good processability. 

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. 

Passivation of the surface of n-GaAs is possible with thin films of plasma polymerized thiophene [255]. A composition containing an electrically nonconductive polymer matrix and 3-octylPT is claimed as a material for parabolic antennas, reflectors for radar, heating systems, photoelectric devices, and electric circuits and apparatus [256]. PTs are used for manufacturing a nonlinear two-terminal device this device is not asymmetrical, gives stable electrical characteristics, and is useful as a display device [257, 258]. PT and 3-octylPT as electrically conductive polymers are claimed to be useful for liquid crystalline display devices [259-261]. PTs are also used for the production of color filters for liquid crystal displays [262]. 

By the sol-gel-process, inorganic glassy and hybrid polymeric materials are accessible at comparatively low temperatures [1], Therefore, organic molecules or dyes can easily be incorporated into the oxide matrix. This combination is especially attractive for the development of the following devices optical filters, solid-state lasers, optical switches, nonlinear optical laser hosts, optical data storage media, and photoconductive devices and films [2]. 

The nonlinear optical and dielectric properties of polymers find increasing use in devices, such as cladding and coatings for optical fibres, piezoelectric and optical fibre sensors, frequency doublers, and thin films for integrated optics applications. It is therefore important to understand the dielectric, optical and mechanical response of polymeric materials to optimize their usage. The parameters that are important to evaluate these properties of polymers are their dipole moment polarizability a, hyperpolarizabilities 0... 

Finally, the combination of dendrimers and organometallic entities as fundamental building blocks affords an opportunity to construct an infinite variety of organometallic starburst polymeric superstructures of nanoscopic, microscopic, and even macroscopic dimensions. These may represent a promising class of organometallic materials due to their specific properties, and potential applications as magnetic ceramic precursors, nonlinear optical materials, and liquid crystal devices in nanoscale technology. 

In the fabrication of practical E-O devices, all of the three critical materials issues (large E-O coefficients, high stability, and low optical loss) need to be simultaneously optimized. One of the major problems encountered in optimizing polymeric E-O materials is to efficiently translate the large P values of organic chromophores into large macroscopic electro-optic activity (r33). According to an ideal-gas model, macroscopic optical nonlinearity should scale as (M is the chromo-... 

In the past decade, much effort has been made to develop polymeric materials possessing simultaneously large EO coefficients, high thermal and photostabilities, and low optical losses, which could be suitable for incorporation into practical EO devices. One major obstacle that limits the development in this area is to efficiently translate high nonlinearities into large macroscopic EO activities. In fact, although the jijj values of chromophores have been improved more than 250-fold, only several... 

An important concern is two-photon absorption which can also become a significant problem at high power densities, especially in the guided wave geometry. These excitations are even more of a problem in multiple quantum well devices and quantum confined structures because direct two-photon absorption can create free carriers which decay very slowly, giving rise to a slow nonlinear response. Molecular and polymeric materials offer additional flexibility to shift the two-photon resonances by chemical modifications. 

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