985 resultados para circular grating
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no. 26-46
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no. 73-104
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no. 105-119
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no. 42-72
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Azobenzene-containing materials exhibit various photomechanical properties, including the formation of surface relief gratings (SRG) when irradiated with two interfering laser beams. In a recent study, a novel glass-forming derivative of Disperse Red 1 (DR1) with a mexylaminotriazine group was synthesized in high yield with a simple and efficient procedure, and showed the ability to form high-quality amorphous thin films with a high resistance to crystallization. Irradiation of films of this material yielded SRG with growth rates comparable to other reported azo materials. Herein, a series of closely related molecular glasses containing azobenzene chromophores with various absorption maxima ranging from 410 to 570 nm were synthesized, and their physical and photomechanical properties were studied. All materials studied showed the ability to form stable glassy phases, and irradiation with lasers emitting at various wavelengths allowed to perform a comparative study of SRG growth within a series of analogous chromophores.
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A chemical sensor based on a coated long-period grating has been prepared and characterized. Designer coatings based on polydimethylsiloxane were prepared by the incorporation of diphenylsiloxane and titanium cross-linker in order to provide enhanced sensitivity for a variety of key environmental pollutants and optimal refractive index of the coating. Upon microextraction of the analyte into the polymer matrix, an increase in the refractive index of the coating resulted in a change in the attenuation spectrum of the long-period grating. The grating was interrogated using ring-down detection as a means to amplify the optical loss and to gain stability against misalignment and power fluctuations. Chemical differentiation of cyclohexane and xylene was achieved and a detection limit of 300 ppm of xylene vapour was realized.
