Photo-induced refraction

From Fig.lOa and Fig.lla, the photo-induced absorption changing spectrum AA(/1) = A (A)-Aq(A) and the photo-induced dichroism spectrum AAd(X.) = Ai(X.)-A//(X.)= lg(T//(X)/T (X)) were obtained, which are shown as solid lines in Fig.lOb and Fig.llb respectively. Assuming that AA and AAd are zero outside of the band 300 800nm, the photo-induced refractive index changing spectrum An(A) = n (A)-iiQ X) and the photo-induced birefringence spectrum Ans(X.) =n X)-n// X) can be calculated according to the Kramers-Kronig relation PI, where jie, tic, ni i and are the refractive indexes of E-form, C-form and of the film... 

When investigating the polar structure by photo-induced light scattering we assume that the largest contribution to the initial optical noise is due to diffraction of the pump beam on optical inhomogeneities located at boundaries of ferroelectric domains [9], Figure 9.12 illustrates this concept schematically. Internal electric fields Ei (random fields) yield local perturbations 5n of the index of refraction via the linear electro-optic effect 5n = - n rssEi. 

Another very promising fabrication process of fluoride glass channel waveguides has been investigated by Davis et al. [256], This process is based on the possibility to create photo-induced modification of the refractive index by a focused, femtosecond IR laser beam. Linear, transparent and colorless marks were formed in the inside of the glass sample translated relatively to the laser beam. Similar experiments were conducted with UV irradiation of PZG fluoride glass thin films [257]. 

Most of the linear optical properties and also some of the nonlinear properties like photo-induced absorption were reported in Section 4.1.2 above. We will here concentrate on phenomenological properties like the refractive index and the second and third order hyperpolarizabilities. 

Photo-induced changes in the complex index of refraction in conjugated polymer/fullerene blends have been reported [148]. 

If the fibre is subjected to any kind of strain or stress, there is a change in refractive index, and consequently there is an induced phase difference between different polarisation directions (this phenomenon is called photo-elastic effect). The change in the refractive index due to stress or strain is also known as induced refractive index (Fidanboylu and Efendioglu, 2009). 

Estimation of Minimai Switching Energy. The estimation of the minimal switching energy for devices utilizing refractive index changes induced by photochromic reactions was carried out in order to evaluate the properties of photo-... 

Recently, semirigid-rod diacrylate compounds were investigated by Hikmet et al. in order to obtain densely crosslinked LC network materials [57] as well as loosely crosslinked anisotropic gel [58-60]. Copolymerization of an LC monoacrylate having a chiral group and LC diacrylate led to a ferroelectric LC network. In a series of papers by Broer et al. [48,49,61,62], highly crosslinked LC networks were prepared by the photopolymerization of diacrylate LC monomers. Photo-polymerization allowed control of the initiation of polymerization and, therefore, the temperature of polymerization. Orientation was induced using surface treatment technique as applied in liquid crystal display, such as a rubbed polyimide film. The resulting ordered networks showed anisotropic behavior in a number of physical properties, such as coefficient of thermal expansion, modulus of elasticity, and refractive index. 

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