Gratings, photoinduced

G. Melt2 and W. W. Morey, "Bragg Grating Formation and GermanosiHcate Fiber Photosensitivity," Proceedings of the SPIE Workshop of on Photoinduced Self-Organisation in OpticalPiber May 10—11, 1991, SPIE, Quebec City, Canada, pp. 185—189. 

PSLCs exhibit a weak dc signal when one beam is incident on the sample that decays over a much longer time scale (a few hours). No such lifetime increase is observed for photorefractive gratings in unpolymerized LCs, which is illustrated by the inset of Fig. 17. These experiments show that a photoinduced process occurs in the PSLCs that encourages charge separation, but also discourages charge recombination. 

The fourth volume of the PET (Photoinduced Electron Transfer) series is again devoted to some fundamental topics. All the chapters present comprehensive reviews. I am very grateful to the authors whose efforts have made this venture possible, especially, since two of them have already contributed to previous issues. 

Diffusion coefficients (D) of various radicals created by the photoinduced hydrogen abstraction reactions from alcohols (ethanol and 2-propanol) as well as those of the parent molecules are measured by using the transient grating (TG) method. Dependence of D on the viscosity, molecular size, and temperature are investigated, and the results are interpreted in terms of microscopic aggregation of the radicals with solvents or solutes. 

Research in the area of photoinduced surface-relief gratings is extremely active. One review covers the literature published until 1998, but the field has practically exploded. One recent paper even reports the creation of a holographic grating with a single short laser pulse, although there are reports questioning the mechanism. ... 

Wu, Y., Natansohn, A., Rochon, P. (2001). Photoinduced birefringence and surface relief gratings in novel polyurethanes with azobenzene groups in the main chain. Macromolecules 34. 7822-7828. 

Sumaru, K., Yamanaka, X, Fukuda, X, and Matsuda, H. Photoinduced surface relief gratings on azopolymer fihn.s . Analysis by a fluid mechanics model. Appl. Phys. Lett. 1999, 75, pp. 1878-1880. 

Hattori, X, Shibata, X, Onodera, S., and Kaino, X Fabrication of refractive index grating into azo-dye-containing polymer films by irreversible photoinduced bleaching. /.. 4pp/. Phys. 2000, 87, pp. 3240-3244. 

Li, X. X, Natansohn, A., and Rochon, P. Photoinduced liquid crystal alignment based on a surface relief grating in an assembled cell. Appl. Phys. Lett. 1999, 74, pp. 3791-3793,... 

Surface-relief grating (SRG, regular topological surface modification) formed via irradiation with an interference pattern of coherent light has been demonstrated only recently/ " and is perhaps the most attractive target in the current research of azo polymers (Chapters 13 and 14 of this book focus on this subject). It is still unclear whether there are any common mechanisms involved between SRG formation and the photomechanical response observed in monolayers described in Section 15.4.1. Nevertheless, with regard to photoinduced motions in Az polymers, it is quite important to proceed with SRG experiments. 

---