Poled host-guest systems

Electrooptic coefficient measured for poled host-guest systems with the chromophore weight percentage in parentheses. 

Electric Field Poling and Photocrosslinking of Host/Guest Systems... 

We mentioned in the previous section that the bulk NLO properties of a poled-polymer host-guest system might be expected to be proportional to the chromophore fi/3 multiplied by the number density of chromophores. However, for high loadings of molecules with large pi, the d33 and r33 coefficients do not continue to increase linearly with chromophore loading, but exhibit maxima these are attributed to competition between the interaction of the chromophores and the poling... 

Fig. 13. Temporal stability of the poled/crosslinked NLO dendrimer 19 and guest/host polymer system (NLO chromophore 16/PQ-lOO) at 85 °C in nitrogen. Normalized rjj as a function of baking time...

Extensive studies have been made on poled NLO guest-host systems . The limited solubility of the NLO species in a host matrix and the thermal relaxation of the induced nonlinear optical activity of the poled polymeric films are major disadvantages. Side chain polymers have attracted attention since a large number of NLO molecules may be covalently attached to the polymer chain and the problem of phase segregation of the NLO component is alleviated. In this article, we present the second and third order NLO properties of a new class of guest-host system which possess excellent doping features and photoreactive characteristics. 

J. P. Drummond, S. J. Clarson, J. S. Zetts, F. K. Hopkinsa, and S. J. Caracci. 1999. Enhanced electro-optic poling in guest-host systems using conductive polymer-based cladding layers. Appl Phys Lett 74(3) 368-370. 

The earliest poled NLO polymeric systems to be investigated were those in which the NLO chromophore was incorporated as a dissolved guest in a polymer host. A variety of guest/host systems have been formulated by incorporating a... 

Polymers incorporating high value chromophores, such as those illustrated in Fig. 3.23, as non-bonded dopants (guest-host systems) have been reported to have r33 values as high as 100 pmV-1. The poled polymers are, however, thermodynamically unstable. The induced non-linearity decays more rapidly for guest-host systems than for systems with covalently attached... 

Dumont and coworkers [136, 155, 156] have observed that shining doped (or functionalized) polymer thin hlms with noncentrosymmetric dipolar chromo-phores, induces a significant increase of electro-optic coefficient in the chromo-phore absorption band, corresponding to a better, polar orientation of chromo-phores. The measurements have been done by using the attenuated total reflection technique, and the optical field polarization was perpendicular to the applied low-frequency external electric field to the thin film (Fig. 33). A better stability of induced orientation was observed in the case of functionalized polymers than in guest-host system, as is usually the case with the static field poled polymers. The chromophores orient with dipolar moments perpendicular to the optical field (and parallel to the applied static (or low frequency) field. As will be discussed later, the chromophore orientation undergoes a trans-cis isomerization process (Fig. 34). 

Molecular dynamics employs Newtonian mechanics to model the time evolution of the system. The positions, velocities, and accelerations of each atom in the system are calculated from the force-field potential. Newtonian mechanics describes the relationship between the potential felt by each atom, the forces on each atom, and, therefore, the accelerations, velocities, and positions of each atom at each time step of the simulation. From the time evolution of the system, we can calculate many properties of the system. In this chapter, we describe the history, methods, and results of the work on the electric field poling of nonlinear optical polymeric guest-host systems. 

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