X-ray investigation of lateral hetero-structures of inversion domains in LiNbO3, KTiOPO4 and KTiOAsO4.

Thomas S Lyford,Stephen P Collins,Paul F Fewster,Pamela A Thomas

doi:10.1107/s2053273315001503

Thomas S Lyford, Stephen P Collins + Show 2 more

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https://doi.org/10.1107/s2053273315001503

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Abstract

In this paper periodically domain-inverted (PDI) ferroelectric crystals are studied using high-resolution X-ray diffraction. Rocking curves and reciprocal-space maps of the principal symmetric Bragg reflections in LiNbO3 (LN) (Λ = 5 µm), KTiOPO4 (KTP) (Λ = 9 µm) and KTiOAsO4 (KTA) (Λ = 39 µm) are presented. For all the samples strong satellite reflections were observed as a consequence of the PDI structure. Analysis of the satellites showed that they were caused by a combination of coherent and incoherent scattering between the adjacent domains. Whilst the satellites contained phase information regarding the structure of the domain wall, this information could not be rigorously extracted without a priori knowledge of the twinning mechanism. Analysis of the profiles reveals strain distributions of Δd/d = 1.6 × 10(-4) and 2.0 × 10(-4) perpendicular to domain walls in KTP and LN samples, respectively, and lateral correlation lengths of 63 µm (KTP), 194 µm (KTA) and 10 µm (LN). The decay of crystal truncation rods in LN and KTP was found to support the occurrence of surface corrugations.

Highlights

Ferroelectrics are non-linear dielectrics that exhibit spontaneous alignment of electric dipoles
In LiNbO3 (LN), KTiOPO4 (KTP) and KTiOAsO4 (KTA), the electric dipoles are aligned with the direction of a polar axis within the structure, and application of a suitable electric field causes the dipoles to reverse their direction, switching the sense of the spontaneous electrical polarization in the crystal
The satellites are identified as being caused by features with a period of Ã, and so are attributed to the periodically domain-inverted (PDI) grating on each sample

Summary

Introduction

Ferroelectrics are non-linear dielectrics that exhibit spontaneous alignment of electric dipoles. By periodically modulating the sense of the spontaneous polarization within the crystal by means of a patterned electrode (Armstrong et al, 1962; Fejer, 1994; Houe & Townsend, 1995), the incident and scattered radiation are quasi-phase matched, allowing good wavelength conversion efficiencies. These periodically domain-inverted (PDI) crystals can be employed in a wide variety of optical devices.

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