Mechanisms for High-Performance and Non-Local Photoisomerization Gratings in a Sol-Gel Material

Autor: Francisco Gallego-Gómez, Francisco del Monte, Klaus Meerholz
Rok vydání: 2013
Předmět:
Zdroj: Digital.CSIC. Repositorio Institucional del CSIC
instname
ISSN: 1616-301X
Popis: Novel azo-containing sol-gel films exhibiting outstanding properties for optical applications via nonlocal photoisomerization gratings were reported recently, although the underlying mechanisms were not well understood, especially regarding the unexpected non-local effect. Here, this photoisomerizable sol-gel material is characterized in-depth, analyzing the design and fabrication strategy, and discussing the aspects that enable the efficient photoresponse, with focus on the holographic recording. The material consists of an azochromophore-rich silica matrix containing glycidoxypropyl groups, which provide increased flexibility and internal free volume for improved dye photoresponse. The matrix characteristics allow a novel procedure for fabrication of thick optical films, in which chromophore aggregation is ruptured by thermal annealing while keeping the material centrosymmetry (beneficial for high hologram contrast). The molecular photo-orientation promotes alignment of microscopic domains in a cooperative motion, not reported previously in sol-gel materials. This collective mechanism enhances the material response and explains some intriguing features of photoisomerization gratings. In particular, there is evidence that spatially shifted domains are related to the grating nonlocal nature. Different recording (write-erase-write) procedures that distinctly affect the photoalignment at both molecular and microscopic level are studied. The holographic performance drastically changes, which can be selectively exploited for either long-term or dynamic holography. The fabrication strategy and underlying mechanisms of a highly photoisomerizable sol-gel material is investigated. Glycidoxypropyl groups and thermal annealing decisively improve the material properties for better dye photoresponse. Molecular photo-orientation promotes cooperative alignment of microscopic domains, enhancing the material response and explaining intriguing features of photoisomerization gratings, such as their potential nonlocal nature. Holographic performance is selectively exploited for either long-term or dynamic holography. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
This work was supported by the European Space Agency (ESA, MAP AO 99-121) and the Germany Ministry of Science and Education (BMBF, project 50WB0730). F.d.M. thanks MAT2009-10214 for financial support.
Databáze: OpenAIRE
Externí odkaz: