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Fabrication of 90-degree domain structures in KNbO3 single crystals
KTH, Superseded Departments, Physics.
2003 (English)In: Ferroelectrics (Print), ISSN 0015-0193, E-ISSN 1563-5112, Vol. 282, 29-36 p.Article in journal (Refereed) Published
Abstract [en]

New domain (90 domain) structure in the KNbO 3 single crystal could be fabricated by applying electric field at room temperature. The coercive electric field of 90 domain is very low (140 V/mm) compared with that of 180 domain (250 V/mm). A very sharp boundary was observed across the whole sample thickness (2 mm). Fabricated 90 domain structures were also confirmed by the (101) surface profile measurement using the optical interferrometer and two peaks of the 404 X-ray diffraction analysis. We also demonstrated the fabrication of periodically 90 domain structures with 200 μ m period without generating unwanted domain structures. As 90 domain structure feels the difference of the refractive index, new applications other than 180 domain will be possible.

Place, publisher, year, edition, pages
2003. Vol. 282, 29-36 p.
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-6112OAI: oai:DiVA.org:kth-6112DiVA: diva2:10730
Note
QC 20100830Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Characterization of domain switching and optical damage properties in ferroelectrics
Open this publication in new window or tab >>Characterization of domain switching and optical damage properties in ferroelectrics
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nonlinear optical frequency conversion is one of the most important key techniques in order to obtain lasers with wavelengths targeted for specific applications. In order to realize efficient and tailored lasers, the quasi-phase-matching (QPM) approach using periodically-poled ferroelectric crystals is getting increasingly important. Also understanding of damage mechanisms in nonlinear materials is necessary to be able to design reliable and well working lasers. This is especially true for high power application lasers, which is a rapidly growing field, where the damage problem normally is the ultimate limiting factor.

In this thesis work, several promising novel ferroelectric materials have been investigated for nonlinear optical applications and the emphasis has been put on QPM devices consisting of periodically-poled structures. The materials were selected from three different types of ferroelectric materials: 1) MgO-doped stoichiometric LiNbO3 (MgO:SLN) and LiTaO3 (MgO:SLT), and non-doped stoichiometric LiTaO3 (SLT), 2) KTiOPO4 (KTP) and its isomorphs RbTiOPO4 (RTP), and 3) KNbO3 (KN). The focus in our investigations have been put on the spontaneous polarization switching phenomena, optimization of the periodic poling conditions, and the photochromic optical damage properties which were characterized by the help of blue light-induced infrared absorption (BLIIRA) measurements.

With electrical studies of the spontaneous polarization switching, we were able to determine quantitatively, and compare, the coercive field values of different materials by applying triangularly shaped electric fields. We found that the values of the coercive fields depended on the increase rate of the applied electric field. The coercive field of KN was the lowest (less than 0.5 kV/mm) followed by the ones of KTP, SLT, and MgO:SLT (1.5 to 2.5 kV/mm). MgO:SLN, and RTP had relatively high coercive fields, approximately 5.0 to 6.0 kV/mm, respectively. Based on the domain switching characteristics we found, we successfully fabricated periodically-poled devices in all of the investigated materials with 30 μm periodicities and sample thickness of 1 mm.

Blue light-induced infrared absorption (BLIIRA) has been characterized for unpoled bulk and periodically-poled samples using a high-sensitivity, thermal-lens spectroscopy technique. SLT showed a large photorefraction effect and the BLIIRA signal could not be properly measured because of the large distortion of the probe beam. The rise and relaxation time of BLIIRA, after switching the blue light on and off was in a time span of 10 to 30 sec except for KTP and its isomorphs, which needed minutes to hours in order to saturate at a fixed value. KN and MgO:SLN showed the lowest susceptibility to the induced absorption. Periodic poling slightly increased the susceptibility of KTP, MgO:SLT, and KN. Relatively high thresholds were observed in MgO:SLT and KN. By increasing the peak-power intensity of the blue light, the induced absorption for MgO:SLN, KTP and KN saturated at a constant value while that of MgO:SLT increase in a constant fashion. This trend is critical issue for the device reliability at high-power applications.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 100 p.
Series
Trita-FYS, ISSN 0280-316X ; 2006:59
Keyword
quasi-phase matching, ferroelectric domains, stoichiometric LiNbO3, stoichiometric LiTaO3, KTiOPO4, KNbO3, polarization switching, periodic electric field poling, optical damages
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-4100 (URN)91-7178-443-8 (ISBN)
Public defence
2006-09-26, Sal FB54, AobaNova univ. centrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100830Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2015-03-30Bibliographically approved

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