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Investigation of electric internal field in congruent LiNbO3 by electro-optic effect
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2004 (English)In: Applied physics letters, ISSN 0003-6951, Vol. 85, 5652-5654 p.Article in journal (Refereed) Published
Abstract [en]

We investigate the effect of the defect-induced internal field on the electro-optic behavior of z-cut congruent lithium niobate crystals. We measure, by a spatially resolved interferometric technique, the phase retardation due to an external applied voltage occurring in two regions with opposite ferroelectric polarization. When measurements are performed just after electrical poling, the two opposite domains show a different electro-optic behavior. We interpret this as due to an elastic component of the internal field. In fact, the asymmetric behavior disappears when the sample is thermally annealed, i.e., when the internal field vanishes

Place, publisher, year, edition, pages
2004. Vol. 85, 5652-5654 p.
Keyword [en]
Lithium-Niobate; Intrinsic Defects; Domain Reversal; Crystals; Nonstoichiometry; Dependence; Origin
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-5822DOI: 10.1063/1.1832738ISI: 000225620100052OAI: oai:DiVA.org:kth-5822DiVA: diva2:10330
Note
QC 20100824Available from: 2006-05-30 Created: 2006-05-30 Last updated: 2010-12-06Bibliographically approved
In thesis
1. Ferroelectric domain engineering and characterization for photonic applications
Open this publication in new window or tab >>Ferroelectric domain engineering and characterization for photonic applications
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Lithium niobate (LiNbO3) and KTiOPO4 (KTP) are ferroelectric crystals of considerable interest in different fields of optics and optoelectronics. Due to its large values of the nonlinear optical, electro-optic (EO), piezoelectric and acousto-optical coefficients, LiNbO3 is widely used for laser frequency conversion using the quasiphase matching (QPM) approach where the sign of nonlinearity has been periodically modulated by electric field poling (EFP). In the microwave and telecommunication field LiNbO3 is used for surface acoustic devices and integrated optical modulators. KTP and its isomorphs, on the other hand, exhibit slightly lower nonlinear coefficients but have much higher photorefractive damage thresholds, so that it is mainly used in the fabrication of QPM devices for both UV, IR and visible light generation and in high power applications.

This thesis focus on different key issues: (1) accurate characterization of specific optical properties of LiNbO3, which are of interest in nonlinear and EO applications; (2) in-situ visualization and characterization of domain reversal by EFP in LiNbO3 and KTP crystals for a through understanding of the ferroelectric domain switching; (3) fabrication of periodic surface structures at sub-micron scale in LiNbO for photonic applications. An interferometric method is used for accurate measurement of ordinary and extraordinary refractive indices in uniaxial crystals, which is of great interest in the proper design of QPM crystals. A digital holography (DH) based method is presented here for 2D characterization of the EO properties of LiNbO , which is considerably interesting in the applications where the proper design of the EO device requires a spatially resolved information about the EO behaviour and the existing pointwise techniques are not sufficient. A DH method for novel in-situ monitoring of domain reversal by EFP in both LiNbO3 and KTP, is also presented here. The technqiue could be used as a tool for high fidelity periodic domain engineering but also provides information about domain kinetics, internal field and crystals defects. 3 3 3 Finally this thesis presents novel results concerning nanoscale periodic surface structuring of congruent LiNbO3. Holographic lithography (HL) is used for sub-micron period resist patterning and electric overpoling for surface domain reversal. Surface structures are obtained by selective etching. Moiré effect is also used in the HL to fabricate complicated structures with multiple periods. The depth compatibility with waveguide implementation allows foreseeing possible applications of these structures for Bragg gratings or innovative photonic crystal devices, exploiting the additional nonlinear and EO properties typical of LiNbO3.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 118 p.
Series
Trita-FYS, ISSN 0280-316X ; 2006:40
Keyword
LiNbO, KTiOPO, interferometry, digital holography, electric field poling, electro-optic materials, holographic lithography, ferroelectric domains, nanostructures, microstructures
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-4001 (URN)91-7178-382-2 (ISBN)
Public defence
2006-06-08, Sal FD5, AlbaNova univ centrum, Roslagstullsbacken 21, Stockholm, 10:00
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Supervisors
Note
QC 20100824Available from: 2006-05-30 Created: 2006-05-30 Last updated: 2015-03-30Bibliographically approved

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