Refractive indices photoinduced changes

Novel all-optical para Bel processing based on photoinduced complex refractive index changes in guided mode thin films... 

B. All-Optical Ultrafast Spatial Light Modulation and Parallel Optical Recording Based on Photoinduced Complex Refractive Index Changes in Guided Wave Geometry Containing Organic Dyes... 

The compound 3-phenyl-anhydro-5-thiolo-l,2,3,4-oxatriazolium oxide 5 (R =Ph) has been incorporated into polymer fdms where its electronic structure and density contribute equally to the measured changes in photoinduced refractive index. Its analogue, 3-phenyl-anhydro-5-hydroxy-l,2,3,4-oxatriazolium oxide 4 (R1=Ph), has been employed as a filter C1999MI6772, 2002MI2290>. 

Another class of photoinduced reactions known to produce large refractive-index changes is the polymerization of diacetylenes (29). These reactions are typically carried out in crystals of the monomer, and result in the production of a fully conjugated polymer backbone. Optical data on these materials are not very extensive, but from what information is available we estimate that nQ 10 22 cm3. (This is for light polarized parallel to the polymer backbone. For the perpendicular polarization the index change is about half as large.)... 

In a photochromie system all of the refractive-index change is a result of photoinduced reactions of isolated molecules, and there is no mass transport over distances larger than molecular dimensions. Since each molecule functions independently, the spatial frequency response of photochromic systems extends from zero to the diffraction limit of the recording light. (This is frequently referred to as "molecular resolution.") While our definition of a photochromic system does not require that the process be reversible, many photochromic systems are reversible, optically and/or thermally (31). In fact, it is in general only with photochromic processes that one can obtain, reversible image recording. 

Ivanov, M., Todorov, T., Nikolova, L., Tomova, N., and Dragostinova, V. Photoinduced changes in the refractive index of azo-dye/polyme systems. Appl. Phys. Lett. 66, 2174... 

The photoinduced phenomenon where the change in refractive index is proportional to the second order term of applied voltage is called an electrooptical Kerr effect. Kerr cells of liquid or solid transparent media can be used together with polarizers to transmit or block light, depending on whether an electric field is applied or not. Such light switches have many uses in laser technology. 

Photochromism is also accompanied by changes in refractive index and dielectric constant. When the photochromic moities are incorporated in polymers, the photoinduced molecular structural change is mirrored at the macroscopic level and leads to interesting properties, such as change in phase transition, viscosity, solubility, wettability, elasticity, and so on [5]. 

Barley SH, Gilbert A, Mitchell GR. 1991. Photoinduced reversible refractive index changes in tailored siloxane based polymers. J Mater Chem 1(3) 481 482. 

Ivanov M, Todorov T, Nikolova L, Tomova N, Dragostinova V. 1995. Photoinduced changes in the refractive index of azo dye/pol5mer systems. Appl Phys Lett 66(17) 2174 2176. 

Shi Y, Steier WH, Yu L, Chen M, Dalton LR. 1991b. Large stable photoinduced refractive index change in a nonlinear optical polyester pol5mier with disperse red side groups. Appl Phys Lett 58(11) 1131 1133. 

Shishido A, et al. 1997. Rapid optical switching by means of photoinduced change in refractive index of azobenzene liquid crystals detected by reflection mode analysis. J Am Chem Soc 119(33) 7791 7796. 

T. Kawakami and N. Sonoda. Photoinduced refractive index change in a photoconductive electrooptical polymer. Appl. Phys. Lett., 62 2167-2169, 1993. 

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