Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Advanced nano- and microdomain engineering of Rb-doped KTiOPO4 for nonlinear optical applications
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fine-pitch ferroelectric domain gratings are extensively used for generation of light in the visible and near-infrared spectral regions through quasi-phase matched (QPM) frequency conversion. Sub-μm QPM devices enables demonstration of nonlinear optics with counterpropagating waves, a field of nonlinear optics which remains sparsely explored due to the difficulty of fabricatinghigh quality gratings.

In recent years, bulk Rb-doped KTiOPO4 (RKTP) has emerged as a highly promising nonlinear materials for fabrication of fine-pitch QPM devices through periodic electric-field poling. RKTP possesses large optical nonlinearity and high resistance to optical damage, while demonstrating improved material homogeneity and lower ionic conductivity than its isomorphs, which are important features for poling. Although fine-pitch QPM gratings, as well as large aperture QPM devices, have been demonstrated, fabrication of sub-μm high quality QPM devices remains a challenge.

The primary aim of this research was to develop a reliable method to fabricate high-quality sub-μm periodically poled RKTP crystals (PPRKTP) and exploit them in novel optical applications. For this purpose, a novel poling method was developed. It was based on periodic modulation of the coercive field through ion exchange, where K+ ions are exchanged with Rb+ in the crystal, to modulate the coercive field and the ionic conductivity. This enables periodic poling of higher quality and with shorter period than ever before.

High quality PPRKTP with a period of 755 nm were fabricated and used to demonstrate the first cascaded mirrorless optical parametric oscillator (MOPO), as well as the first MOPO pumped by a Q-switched laser. PPRKTP samples for blue light generation were fabricated, and second harmonic generation (SHG) was investigated with a high power 946 nm fiber laser. Up to 2 W of blue power was demonstrated for bulk samples, where the output power was limited by absorption of the SHG, leading to thermal dephasing of the devices. Laser-written waveguides were fabricated in PPRKTP for the first time, and a record high SHG power of 76 mW was obtained.

Finally, the high-temperature stability of ferroelectric domain gratings was investigated. This is of utmost importance when a PPRKTP crystal is used as a seed for crystal growth. It was found that for charged domains walls, the domain-wall motion was highly anisotropic with rapid movement in y-direction while only small movements were observed in the x-direction of the crystal.

Abstract [sv]

Ickelinjära ferroelektriska kristaller med artificiella domängitter med perioder av några mikrometer används idag för generering av ljus i de synliga och nära-infraröda våglängdsområdena, genom kvasifasmatchad (QPM) frekvenskonvertering. Med sub-μm QPM domängitter kan man åstadkomma ickelinjära optiska effekter med motpropagerande parametriska ljusvågor. Detta är ett område av den ickelinjära optiken som fortfarande är tämligen outforskat på grund av svårigheten med att tillverka högkvalitativa domängitter.

 Under de senaste åren har Rb-dopat KTiOPO4 (RKTP) blivit ett mycket lovande ickelinjärt material för tillverkning av QPM-gitter med mycket korta perioder genom periodisk elektrisk fält polning. RKTP kristallen har en hög optisk ickelinejäritet och den tål höga optiska intensiteter, samtidigt som materialet har bättre materialhomogenitet och lägre jonledningsförmåga än vad dess isomorfa kristaller har. De två senare egenskaperna har visat sig viktiga för att få en lyckad polning. Fastän QPM-gitter med kort periodicitet, liksom QPM-gitter med stor apertur, har demonstrerats, är tillverkningen av högkvalitativa QPM-kristaller med sub-µm perioder fortfarande en utmaning.

Det primära syftet med denna avhandling var att utveckla en pålitlig metod för att tillverka högkvalitativa sub-μm periodiskt polade RKTP kristaller (PPRKTP) och utnyttja dem i nya optiska tillämpningar. I detta syfte utvecklades en ny polningsmetod. Den baseras på periodiskt jonutbyte, där K+ joner byts mot Rb+ i kristallen, vilket resulterar i en samtidig modulation av materialets koerciva fält och jonledningsförmåga. Detta möjliggör i sin tur periodisk polning av högre kvalitet och med kortare perioder än någonsin tidigare har uppnåtts.

Högkvalitativa PPRKTP kristaller med en period på 755 nm tillverkades och användes för att demonstrera den första kaskaderade spegelfria optiska parametriska oscillatorn (MOPO), liksom den första MOPO processen pumpad av en Q-switchad laser. Vidare utvecklades PPRKTP-kristaller för generering av blått ljus via frekvensdubbling. Dessa utvärderades med hjälp av en högeffekts-fiberlaser vid 946 nm. Upp till 2 W av blått ljus erhölls för bulkkristallerna. Uteffekten begränsades av absorption av det blåa frekvensdubblade ljuset, vilket ledde till urfasning i QPM-gittret p.g.a. termiska effekter. Laserskrivna vågledare tillverkades sedan i PPRKTP för första gången, och en rekordhög effekt på 76 mW erhölls via frekvensdubbling.

Slutligen undersöktes stabiliteten hos de periodiskt polade domängitterna vid höga temperaturer. Det är viktigt att domängittrena är stabila när PPRKTP kristallerna används som ympämne för kristalltillväxt. Det visade sig att instabila domänväggar flyttade sig mycket anisotropt, med en snabb rörelse i kristallens y-riktning och en långsam rörelse i kristallens x-riktning.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. , 97 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2017:29
Keyword [en]
KTiOPO4, nonlinear optics, MOPO, quasi-phase matching, SHG, ferroelectrics, domain structuring, periodic poling
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-207161ISBN: 978-91-7729-413-9 (print)OAI: oai:DiVA.org:kth-207161DiVA: diva2:1096459
Public defence
2017-06-15, FA32, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20170519

Available from: 2017-05-19 Created: 2017-05-17 Last updated: 2017-05-19Bibliographically approved
List of papers
1. Periodic poling of Rb-doped KTiOPO4 by coercive field engineering
Open this publication in new window or tab >>Periodic poling of Rb-doped KTiOPO4 by coercive field engineering
2016 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 13, 14682-14689 p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate fine-pitch periodic poling of bulk Rb-doped KTiOPO4 using a coercive field grating induced by ion-exchange. These samples were used for quasi phase matched (QPM) second harmonic generation at 795 nm with a normalized conversion efficiency of 1.7% W−1cm−1. Additionally, the ion-exchange introduced a refractive index change over the sample thickness resulting in a phasematching wavelength shift of 0.21 nm, adding extra tunability to the QPM device.

Place, publisher, year, edition, pages
Optical Society of America, 2016
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-188943 (URN)10.1364/OE.24.014682 (DOI)000381759800087 ()2-s2.0-84977641101 (Scopus ID)
Note

QC 20160712

Available from: 2016-06-22 Created: 2016-06-22 Last updated: 2017-05-17Bibliographically approved
2. Cascaded counter-propagating nonlinear interactions inhighly-efficient sub-μm periodically poled crystals
Open this publication in new window or tab >>Cascaded counter-propagating nonlinear interactions inhighly-efficient sub-μm periodically poled crystals
Show others...
(English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
Nature Publishing Group
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-207158 (URN)
Note

QC 20170602

Available from: 2017-05-17 Created: 2017-05-17 Last updated: 2017-06-02Bibliographically approved
3. A highly efficient mirrorless optical parametricoscillator pumped by nanosecond pulses
Open this publication in new window or tab >>A highly efficient mirrorless optical parametricoscillator pumped by nanosecond pulses
(English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794Article in journal (Refereed) Submitted
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-207159 (URN)
Note

QC 21070519

Available from: 2017-05-17 Created: 2017-05-17 Last updated: 2017-05-19Bibliographically approved
4. Thermal stability of ferroelectric domain gratings in Rb-doped KTP
Open this publication in new window or tab >>Thermal stability of ferroelectric domain gratings in Rb-doped KTP
Show others...
2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 8, 082906Article in journal (Refereed) Published
Abstract [en]

We study the thermal stability of domain walls in periodically poled Rb-doped KTP crystals. Domain-wall motion is observed after annealing the crystals above 550 degrees C. This motion is highly anisotropic along the a- and b- crystallographic axes. Along the b-axis domain wall motion is in the order of tens of micrometers. In the a-direction, it results in either three orders of magnitude smaller domain wall displacement or in domain merging, depending on the initial domain configuration. We show that the thermal stability of the domain gratings depends on their periodicity, resulting in complete backswitching for sub-micrometer domains annealed at 730 degrees C.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-173981 (URN)10.1063/1.4929817 (DOI)000360593900056 ()2-s2.0-84940524547 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20151005

Available from: 2015-10-05 Created: 2015-09-24 Last updated: 2017-05-17Bibliographically approved
5. Highly efficient continuous wave blue second-harmonic generation in fs-laser written periodically poled Rb:KTiOPO4 waveguides
Open this publication in new window or tab >>Highly efficient continuous wave blue second-harmonic generation in fs-laser written periodically poled Rb:KTiOPO4 waveguides
Show others...
2014 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, no 5, 1274-1277 p.Article in journal (Refereed) Published
Abstract [en]

Waveguides were inscribed into a 9.5 mm long periodically poled KTiOPO4 crystal with a Ti:sapphire femtosecond-laser. Waveguiding was achieved between two parallel written tracks with spacings of 17–19 μm. The fundamental power of 1.6 W for frequency doubling in the waveguide was delivered by a continuous wave Ti:sapphire laser at a wavelength of 943.18 nm. A maximum output power of 76 mW in the blue spectral region was achieved. This corresponds to a single pass normalized conversion efficiency of 4.6%  W−1 cm−2.

Keyword
Femtosecond-Laser, Induced Breakdown, Slope Efficiency, Diode-Laser, Ktp, Light, Ktiopo4, Power, Crystal
National Category
Engineering and Technology
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143203 (URN)10.1364/OL.39.001274 (DOI)000332233300044 ()2-s2.0-84897400572 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20140331

Available from: 2014-03-18 Created: 2014-03-18 Last updated: 2017-05-17Bibliographically approved
6. High power single-crystal fiber CW 946 nm laser and blue generation based on Rubidium-doped PPKTP
Open this publication in new window or tab >>High power single-crystal fiber CW 946 nm laser and blue generation based on Rubidium-doped PPKTP
Show others...
2013 (English)In: 2013 Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, IEEE conference proceedings, 2013Conference paper, Published paper (Refereed)
Abstract [en]

Blue lasers have numerous applications in spectroscopy, underwater communication and material processing. Direct emission in the blue region can be achieved with laser diodes, with powers up to the watt level [1]. Higher powers require efficient laser operating around 950 nm to be frequency doubled to the blue spectrum, which usually suffer from a lower gain than conventional 1μm lasers. Generally, intracavity frequency doubling set-ups and pulsed operation are used to increase the second harmonic generation efficiency, with output powers up to 4 W in cw[2] and 1.3W in pulsed regime [3]. In the past few years, both lasers materials and non linear crystals have progressed enough to allow the very simple extracavity frequency doubling of continuous wave lasers in periodically poled materials to acceptable powers[4].

Place, publisher, year, edition, pages
IEEE conference proceedings, 2013
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143910 (URN)10.1109/CLEOE-IQEC.2013.6800605 (DOI)000355316300014 ()2-s2.0-84900302399 (Scopus ID)
Conference
2013 Conference on Lasers and Electro-Optics - International Quantum Electronics Conference
Note

QC 20150210

Available from: 2014-04-02 Created: 2014-04-02 Last updated: 2017-05-17Bibliographically approved

Open Access in DiVA

fulltext(3504 kB)62 downloads
File information
File name FULLTEXT01.pdfFile size 3504 kBChecksum SHA-512
99ab3d83ab9797d7558668332a51dd6a0702de2bd9090c1749acf493c606642e7ee2089535ef546cf77c113a89fac07e52baf456fa82a840e8a83f32cc65545d
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Liljestrand, Charlotte
By organisation
Laser Physics
Atom and Molecular Physics and Optics

Search outside of DiVA

GoogleGoogle Scholar
Total: 62 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 149 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf