Switchable Bragg gratings based on soft materials

Vita, Francesco (2006) Switchable Bragg gratings based on soft materials. [Tesi di dottorato] (Inedito)

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Abstract

Topic of the thesis is the study of diffraction Bragg gratings holographically recorded in polymer-liquid crystal composite materials. Due to the special electro-optical properties of liquid crystals, these gratings can be electrically driven, switching between a diffraction and a transmission state. In the present work, techniques and materials used to produce such gratings are described, with emphasis on the connections between the final morphology and the preparation procedure, materials and exposure. Different types of gratings have been characterized, both in the visible and in the near infrared range, in view of a possible use as photonic devices in the optical communication systems. Grating diffraction efficiency has been measured varying the wavelength, the temperature, the angle of incidence and the applied electric field. The behavior in dynamic conditions has been analyzed by measuring switching times for electric pulse of variable amplitude and duration. These measurements have been analyzed with suitable mathematical models and related to the morphology of the studied materials, like the interface between polymer and liquid crystal, anisotropy of liquid crystal domains and the degree of phase separation. Results obtained provide a deeper insight into the structure of such materials and make possible the optimization of their properties and the design of different photonic devices. Finally, the use of variable angle ellipsometry and /or half-leaky guide mode technique to measure soft material optical properties is discussed.

Tipologia di documento:Tesi di dottorato
Parole chiave:Polymer dispersed liquid crystals, Bragg gratings, Optics
Settori scientifico-disciplinari MIUR:Area 02 Scienze fisiche > FIS/03 FISICA DELLA MATERIA
Coordinatori della Scuola di dottorato:
Coordinatore del Corso di dottoratoe-mail (se nota)
Tagliacozzo, Arturo
Tutor della Scuola di dottorato:
Tutor del Corso di dottoratoe-mail (se nota)
Abbate, Giancarlo
Stato del full text:Accessibile
Data:2006
Numero di pagine:107
Istituzione:Università degli Studi di Napoli Federico II
Dipartimento o Struttura:Scienze Fisiche
Tipo di tesi:Dottorato
Stato dell'Eprint:Inedito
Denominazione del dottorato:Fisica Fondamentale ed Applicata
Ciclo di dottorato:XVIII
Numero di sistema:617
Depositato il:01 Agosto 2008
Ultima modifica:04 Febbraio 2009 09:39

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