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Characterization of domain switching and optical damage properties in ferroelectrics
KTH, School of Engineering Sciences (SCI), Physics.
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. , p. 100
Series
Trita-FYS, ISSN 0280-316X ; 2006:59
Keyword [en]
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: urn:nbn:se:kth:diva-4100ISBN: 91-7178-443-8 (print)OAI: oai:DiVA.org:kth-4100DiVA, id: diva2:10734
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
List of papers
1. Polarization switching characteristics of flux grown KTiOPO4 and RbTiOPO4 at room temperature
Open this publication in new window or tab >>Polarization switching characteristics of flux grown KTiOPO4 and RbTiOPO4 at room temperature
2005 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, no 12, p. 124105-Article in journal (Refereed) Published
Abstract [en]

A study of polarization-switching characteristics under an applied electrical field at room temperature is presented for flux-grown KTiOPO4 and RbTiOPO4. By optimizing the experimental conditions, we determined the coercive field and the domain-switching time quantitatively by direct observation of the switching current. For both isomorphs, the inverse of the polarization-switching time, 1/t(s), follows an exponential dependence on the applied field E in low-field regime, and a linear dependence on E in the high-field regime. Domain morphology of KTiOPO4 based on selective etching reveals laminar structures elongated in the b crystallographic direction. An estimation of the domain-wall velocity shows that the domain speed in the polar direction is, at least, two orders of magnitude larger than in the a-b plane. The velocity along the b direction is similar to 30 times larger than along the a axis.

Keyword
electrooptic imaging microscopy, potassium titanyl phosphate, periodically poled ktiopo4, lithium tantalite, ionic-conductivity, internal field, electric-field, blue-light, ferroelectric domains, single-crystals
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7992 (URN)10.1063/1.1940135 (DOI)000230278100083 ()2-s2.0-21644435070 (Scopus ID)
Note
QC 20100830Available from: 2005-10-25 Created: 2005-10-25 Last updated: 2017-12-14Bibliographically approved
2. Embryonic nucleation method for fabrication of uniform periodically poled structures in potassium niobate for wavelength conversion devices
Open this publication in new window or tab >>Embryonic nucleation method for fabrication of uniform periodically poled structures in potassium niobate for wavelength conversion devices
2004 (English)In: Japanese journal of applied physics, ISSN 0021-4922, Vol. 43, no 2, p. 559-566Article in journal (Refereed) Published
Abstract [en]

A new electric poling concept called the 'embryonic nucleation method' for the fabrication of periodically poled structures has been proposed. By applying this method to KNbO3, 1-mm-thick uniform periodically poled KNbO3 (PPKN) with domain inverted period of 35.5 mum and an interaction length of 10 mm has been successfully fabricated by applying only 300 V/mm without the generation of unwanted domains. Furthermore, the reproducibility of the periodic poling process has been greatly improved. SHG using PPKN fabricated by this method was demonstrated and 100 mW second-harmonic laser generation at a wavelength of 532 nm was obtained from 1 W pumping without photorefractive damage at approximately 40 degrees C.

Keyword
periodically poled; domain inversion; potassium niobate; electrical poling; wavelength conversion
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-6110 (URN)10.1143/JJAP.43.559 (DOI)000220401000026 ()
Note
QC 20100830Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2010-12-06Bibliographically approved
3. Controllability of specific domain structures in KNbO3 single crystals by electric poling at room temperature
Open this publication in new window or tab >>Controllability of specific domain structures in KNbO3 single crystals by electric poling at room temperature
Show others...
2005 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, no 034107, p. 034107-Article in journal (Refereed) Published
Abstract [en]

The controllability of specific domain structures in KNbO3 single crystals was investigated by electric poling to several different orientations at room temperature. By applying electric field to the direction corresponding to the differetial direction between the original and intended spontaneous polarization directions (differential vector poling method), 60°-, 90°-, and 180°-domain pairs were successfully fabricated under control in KNbO3. The measured threshold electric field for 90°-domain pairs was the lowest (140 V/mm), which could be related to the difference between the piezoelectric coefficients of the poling direction. For 60°- and 90°-domain pairs, theoretical uncharged domain walls fabricated under control without the generation of other domain structures. For 120°-domain pairs, (011)pc uncharged domain wall was not observed, which suggests the difficulty in generating uncharged 120°-domain walls without passing through the phase transition.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6111 (URN)10.1063/1.2001148 (DOI)000231246100082 ()
Note
QC 20110203Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2017-12-14Bibliographically approved
4. Fabrication of 90-degree domain structures in KNbO3 single crystals
Open this publication in new window or tab >>Fabrication of 90-degree domain structures in KNbO3 single crystals
2003 (English)In: Ferroelectrics (Print), ISSN 0015-0193, E-ISSN 1563-5112, Vol. 282, p. 29-36Article 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.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-6112 (URN)
Note
QC 20100830Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2017-12-14Bibliographically approved
5. Quasi-phase-matched frequency conversion in KNbO3 structures consisting of 90-degree ferroelectric domains
Open this publication in new window or tab >>Quasi-phase-matched frequency conversion in KNbO3 structures consisting of 90-degree ferroelectric domains
2005 (English)In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 81, p. 761-763Article in journal (Refereed) Published
Abstract [en]

Periodic 90° domain structure with 18.6 μm periodicity was fabricated by applying a 200 V/mm electric field over (1̄01)-cut KNbO3 plate. The blue light generation by quasi-phase-matched frequency doubling in this periodic 90° domain structure is demonstrated. The 90° domain structure completely compensates for a Poynting vector walk-off of the second-harmonic beam. Moreover, these structures exhibit amphoteric Poynting vector refraction properties, i.e., the refraction can be negative or positive depending on the angle of incidence at the 90° domain boundary.

Keyword
periodically-poled linbo3, optical parametric oscillation, orthorhombic knbo3; potassium niobate, single-crystals, refractive-indexes, fabrication, generation
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-6113 (URN)10.1007/s00340-005-1956-5 (DOI)000232792500004 ()2-s2.0-27244448969 (Scopus ID)
Note
QC 20100830Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2017-12-14Bibliographically approved
6. Total refraction of p-polarized light at the 90-degree domain boundary in the ferroelectric crystal
Open this publication in new window or tab >>Total refraction of p-polarized light at the 90-degree domain boundary in the ferroelectric crystal
2004 (English)In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 43, no 6A, p. 3413-3418Article in journal (Refereed) Published
Abstract [en]

A 90.DEG.-domain structure was fabricated using electrical poling in ferroelectric birefringent KNbO3 crystal. The refraction and reflection characteristics of the light at the boundary of the 90.DEG.-domain structure were investigated, and the novel behavior of total refraction (no reflection) has been found for the P-polarized light throughout the entire range of incident angle (0.LEQ..THETA..LEQ.90.DEG.). Strong refraction of the light was observed after it exited from the crystal output surface at the incidence parallel to the domain boundary. These behaviors were explained analytically. (author abst.)

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6114 (URN)10.1143/JJAP.43.3413 (DOI)000222503400030 ()
Note
QC 20110211Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2017-12-14Bibliographically approved
7. Picosecond blue light-induced infrared absorption in single-domain and periodically poled ferroelectrics
Open this publication in new window or tab >>Picosecond blue light-induced infrared absorption in single-domain and periodically poled ferroelectrics
2007 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 033105Article in journal (Refereed) Published
Abstract [en]

Picosecond blue-light-induced infrared absorption is investigated in bulk and periodically poled ferroelectrics known to have high photorefractive resistance (KTiOPO4, MgO-doped congruent LiNbO3, MgO-doped stoichiometric LiNbO3, MgO-doped stoichiometric LiTaO3, and KNbO3). KNbO3 and MgO-doped congruent and stoichiometric LiNbO3 show the lowest susceptibility to induced absorption. Periodic poling slightly increases the susceptibility to the induced absorption in all materials but most noticeably in KTiOPO4, MgO-doped stoichiometric LiTaO3, and KNbO3. Different dynamics of induced absorption are investigated. Relatively high thresholds for induced absorption were observed in MgO-doped stoichiometric LiTaO3 and KNbO3. By increasing the peak power intensity of blue light, the induced absorption for LiNbO3, KTiOPO4, and KNbO3 are saturated, while in MgO-doped stoichiometric LiTaO3, the induced absorption increases almost linearly with the blue peak intensity. The low susceptibility to induced absorption observed in KNbO3 corroborates well with the earlier proposed existence of very shallow traps close to the valence band.

Keyword
stoichiometric litao3, refractive-indexes, potassium niobate, lithium tantalite, doped linbo3, ktiopo4, knbo3, crystals, devices, ktp
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-6115 (URN)10.1063/1.2434007 (DOI)000244250100005 ()2-s2.0-33847156833 (Scopus ID)
Note
QC 20100830Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2017-12-14Bibliographically approved

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