lithium niobate

Lithium niobate is a colorless solid, and it is insoluble in water. It has a trigonal crystal system, which lacks inversion symmetry and displays ferroelectricity, the Pockels effect, the piezoelectric effect, photoelasticity and nonlinear optical polarizability. Lithium niobate has negative uniaxial birefringence which depends slightly on the stoichiometry of the crystal and on temperature. It is transparent for wavelengths between 350 and 5200 nanometers.

Lithium niobate can be doped with magnesium oxide, which increases its resistance to optical damage (also known as photorefractive damage). Other available dopants are iron, zinc, hafnium, copper, gadolinium, erbium, yttrium, manganese and boron.

File:Lithium Niobate Wafer.jpg

Single crystals of lithium niobate can be grown using the Czochralski process.{{cite book|title = Lithium Niobate: Defects, Photorefraction and Ferroelectric Switching|first = Tatyana|last = Volk|author2=Wohlecke, Manfred |publisher = Springer|year = 2008|isbn = 978-3-540-70765-3|doi=10.1007/978-3-540-70766-0|pages=1–9}}

After a crystal is grown, it is sliced into wafers of different orientation. Common orientations are Z-cut, X-cut, Y-cut, and cuts with rotated angles of the previous axes.{{cite book|last=Wong|first=K. K.|title=Properties of Lithium Niobate|year=2002|publisher=INSPEC|location=London, United Kingdom|isbn=0-85296-799-3|pages=8}}

Thin-film lithium niobate (e.g. for optical wave guides) can be transferred to or grown on sapphire and other substrates, using the smart cut (ion slicing) process{{Cite journal |last1=Levy |first1=M. |last2=Osgood |first2=R. M. |last3=Liu |first3=R. |last4=Cross |first4=L. E. |last5=Cargill |first5=G. S. |last6=Kumar |first6=A. |last7=Bakhru |first7=H. |date=1998-10-19 |title=Fabrication of single-crystal lithium niobate films by crystal ion slicing |url=http://aip.scitation.org/doi/10.1063/1.121801 |journal=Applied Physics Letters |language=en |volume=73 |issue=16 |pages=2293–2295 |doi=10.1063/1.121801 |bibcode=1998ApPhL..73.2293L |issn=0003-6951}}{{Cite journal |title= Enhanced electro-optical lithium niobate photonic crystal wire waveguide on a smart-cut thin film|url=https://opg.optica.org/oe/viewmedia.cfm?uri=oe-20-3-2974&html=true |access-date=2022-07-08 |journal=Optics Express | year=2012 |doi=10.1364/oe.20.002974| pmid=22330535 | last1=Lu | first1=H. | last2=Sadani | first2=B. | last3=Courjal | first3=N. | last4=Ulliac | first4=G. | last5=Smith | first5=N. | last6=Stenger | first6=V. | last7=Collet | first7=M. | last8=Baida | first8=F. I. | last9=Bernal | first9=M. P. | volume=20 | issue=3 | pages=2974–2981 | doi-access=free }} or MOCVD process.{{cite journal|doi=10.1016/0022-0248(95)00570-6|title=Epitaxial growth of lithium niobate thin films by the solid source MOCVD method |year=1996 |last1=Feigelson |first1=R. S. |journal=Journal of Crystal Growth |volume=166 |issue=1–4 |pages=1–16 |bibcode=1996JCrGr.166....1F |doi-access=free }} The technology is known as lithium niobate on insulator (LNOI).{{cite book|chapter-url=https://physik.uni-paderborn.de/fileadmin/physik/Alumni/Sohler/2012/SPIE_Photonics_Europe_Hu__LNOI_2012.pdf |doi=10.1117/12.922401 |chapter=Lithium niobate-on-insulator (LNOI): Status and perspectives |title=Silicon Photonics and Photonic Integrated Circuits III |year=2012 |last1=Hu |first1=Hui |last2=Yang |first2=Jin |last3=Gui |first3=Li |last4=Sohler |first4=Wolfgang |volume=8431 |pages=84311D |s2cid=120452519 }}

Nanoparticles of lithium niobate and niobium pentoxide can be produced at low temperature.{{cite journal |author1=Grange, R. |author2=Choi, J.W. |author3=Hsieh, C.L. |author4=Pu, Y. |author5=Magrez, A. |author6=Smajda, R. |author7=Forro, L. |author8=Psaltis, D. |title=Lithium niobate nanowires: synthesis, optical properties and manipulation |journal=Applied Physics Letters |volume=95 |issue=14 |pages=143105 |year=2009 |url=http://link.aip.org/link/?APPLAB/95/143105/1 |doi=10.1063/1.3236777 |bibcode=2009ApPhL..95n3105G |url-status=dead |archive-url=http://arquivo.pt/wayback/20160514132623/http://link.aip.org/link/?APPLAB/95/143105/1 |archive-date=2016-05-14 }} The complete protocol implies a LiH induced reduction of NbCl₅ followed by in situ spontaneous oxidation into low-valence niobium nano-oxides. These niobium oxides are exposed to air atmosphere resulting in pure Nb₂O₅. Finally, the stable Nb₂O₅ is converted into lithium niobate LiNbO₃ nanoparticles during the controlled hydrolysis of the LiH excess.{{cite journal|vauthors=Aufray M, Menuel S, Fort Y, Eschbach J, Rouxel D, Vincent B |title = New Synthesis of Nanosized Niobium Oxides and Lithium Niobate Particles and Their Characterization by XPS Analysis|journal = Journal of Nanoscience and Nanotechnology|volume = 9|issue = 8|pages = 4780–4789|year = 2009|doi = 10.1166/jnn.2009.1087|pmid = 19928149|citeseerx = 10.1.1.465.1919}} Spherical nanoparticles of lithium niobate with a diameter of approximately 10 nm can be prepared by impregnating a mesoporous silica matrix with a mixture of an aqueous solution of LiNO₃ and NH₄NbO(C₂O₄)₂ followed by 10 min heating in an infrared furnace.{{cite journal|author1=Grigas, A |author2=Kaskel, S |title = Synthesis of LiNbO₃ nanoparticles in a mesoporous matrix |journal = Beilstein Journal of Nanotechnology|volume = 2|pages = 28–33|year = 2011|doi =10.3762/bjnano.2.3|pmid=21977412 |pmc=3045940 }}

Lithium niobate is used extensively in the telecommunications market, e.g. in mobile telephones and optical modulators.{{cite book|title = Lithium Niobate Photonics|first = James|last = Toney |publisher = Artech House|year = 2015|isbn = 978-1-60807-923-0}} Due to its large electro-mechanical coupling, it is the material of choice for surface acoustic wave (SAW) devices.{{cite journal |last1=Gruenke |first1=Rachel |last2=Hitchcock |first2=Oliver |year=2024 |title=Surface modification and coherence in lithium niobate SAW resonators |journal=Scientific Reports |volume=14 |page=6663 |doi=10.1038/s41598-024-57168-x}} For some uses it can be replaced by lithium tantalate. Other uses are in laser frequency doubling, nonlinear optics, Pockels cells, optical parametric oscillators, Q-switching devices for lasers, other acousto-optic devices, optical switches for gigahertz frequencies, etc. It is an excellent material for manufacture of optical waveguides. It's also used in the making of optical spatial low-pass (anti-aliasing) filters. Additionally, it is used in pyroelectric infrared (IR) detectors, where it detects temperature changes by generating electric charges.{{cite web |url=https://www.samaterials.com/niobium-compounds/66-lithium-niobate-wafers.html |title=CY0066 Lithium Niobate Wafers (LiNbO3 Wafers) |website=Stanford Advanced Materials |access-date=Oct 18, 2024}}

In the past few years lithium niobate is finding applications as a kind of electrostatic tweezers, an approach known as optoelectronic tweezers as the effect requires light excitation to take place.{{cite journal | last1=Carrascosa | first1=M. | last2=García-Cabañes | first2=A. | last3=Jubera | first3=M. | last4=Ramiro | first4=J. B. | last5=Agulló-López | first5=F. | title=LiNbO₃: A photovoltaic substrate for massive parallel manipulation and patterning of nano-objects | journal=Applied Physics Reviews | publisher=AIP Publishing | volume=2 | issue=4 | year=2015 | issn=1931-9401 | doi=10.1063/1.4929374 | page=040605| bibcode=2015ApPRv...2d0605C | hdl=10486/669584 | hdl-access=free }}{{cite journal | last1=García-Cabañes | first1=Angel | last2=Blázquez-Castro | first2=Alfonso | last3=Arizmendi | first3=Luis | last4=Agulló-López | first4=Fernando | last5=Carrascosa | first5=Mercedes | title=Recent Achievements on Photovoltaic Optoelectronic Tweezers Based on Lithium Niobate | journal=Crystals | publisher=MDPI AG | volume=8 | issue=2 | date=2018-01-30 | issn=2073-4352 | doi=10.3390/cryst8020065 | page=65| doi-access=free | hdl=10486/681685 | hdl-access=free }} This effect allows for fine manipulation of micrometer-scale particles with high flexibility since the tweezing action is constrained to the illuminated area. The effect is based on the very high electric fields generated during light exposure (1–100 kV/cm) within the illuminated spot. These intense fields are also finding applications in biophysics and biotechnology, as they can influence living organisms in a variety of ways.{{cite journal | last1=Blázquez-Castro | first1=A. | last2=García-Cabañes | first2=A. | last3=Carrascosa | first3=M. | title=Biological applications of ferroelectric materials | journal=Applied Physics Reviews | publisher=AIP Publishing | volume=5 | issue=4 | year=2018 | issn=1931-9401 | doi=10.1063/1.5044472 | page=041101| arxiv=2109.00429 | bibcode=2018ApPRv...5d1101B | s2cid=139511670 }} For example, iron-doped lithium niobate excited with visible light has been shown to produce cell death in tumoral cell cultures.{{cite journal | last1=Blázquez-Castro | first1=Alfonso | last2=Stockert | first2=Juan C. | last3=López-Arias | first3=Begoña | last4=Juarranz | first4=Angeles | last5=Agulló-López | first5=Fernando | last6=García-Cabañes | first6=Angel | last7=Carrascosa | first7=Mercedes | title=Tumour cell death induced by the bulk photovoltaic effect of LiNbO₃:Fe under visible light irradiation | journal=Photochemical & Photobiological Sciences | publisher=Springer Science and Business Media LLC | volume=10 | issue=6 | year=2011 | pages=956–963 | issn=1474-905X | doi=10.1039/c0pp00336k | pmid=21336376 | doi-access=free }}

Periodically poled lithium niobate (PPLN) is a domain-engineered lithium niobate crystal, used mainly for achieving quasi-phase-matching in nonlinear optics. The ferroelectric domains point alternatively to the +c and the −c direction, with a period of typically between 5 and 35 μm. The shorter periods of this range are used for second-harmonic generation, while the longer ones for optical parametric oscillation. Periodic poling can be achieved by electrical poling with periodically structured electrode. Controlled heating of the crystal can be used to fine-tune phase matching in the medium due to a slight variation of the dispersion with temperature.

Periodic poling uses the largest value of lithium niobate's nonlinear tensor, d₃₃ = 27 pm/V. Quasi-phase-matching gives maximum efficiencies that are 2/π (64%) of the full d₃₃, about 17 pm/V.{{cite journal |doi=10.1007/s003400100623 |title=Fabrication of periodically poled lithium tantalate for UV generation with diode lasers |journal=Applied Physics B |volume=73 |issue=2 |pages=111–114 |year=2001 |last1=Meyn |first1=J.-P. |last2=Laue |first2=C. |last3=Knappe |first3=R. |last4=Wallenstein |first4=R.|last5=Fejer |first5=M. M. |bibcode=2001ApPhB..73..111M |s2cid=119763435}}

Other materials used for periodic poling are wide-band-gap inorganic crystals like KTP (resulting in periodically poled KTP, PPKTP), lithium tantalate, and some organic materials.

The periodic-poling technique can also be used to form surface nanostructures.{{cite journal |title=Surface nanoscale periodic structures in congruent lithium niobate by domain reversal patterning and differential etching |journal=Applied Physics Letters |volume=87 |issue=23 |pages=233106 |year=2005 |doi=10.1063/1.2137877|bibcode=2005ApPhL..87w3106G |last1=Grilli |first1=Simonetta |last2=Ferraro |first2=Pietro |last3=De Natale |first3=Paolo |last4=Tiribilli |first4=Bruno |last5=Vassalli |first5=Massimo |doi-access=free }}{{cite journal |title=Modulating the thickness of the resist pattern for controlling size and depth of submicron reversed domains in lithium niobate |journal=Applied Physics Letters |volume=89 |issue=13 |pages=133111 |year=2006 |doi=10.1063/1.2357928| bibcode =2006ApPhL..89m3111F |last1=Ferraro |first1=P. |last2=Grilli |first2=S. }}

However, due to its low photorefractive damage threshold, PPLN only finds limited applications, namely, at very low power levels. MgO-doped lithium niobate is fabricated by periodically poled method. Periodically poled MgO-doped lithium niobate (PPMgOLN) therefore expands the application to medium power level.

The Sellmeier equations for the extraordinary index are used to find the poling period and approximate temperature for quasi-phase-matching. Jundt{{cite journal |author=Jundt, Dieter H. |journal=Optics Letters |volume=22 |title=Temperature-dependent Sellmeier equation for the index of refraction $n\_e$ in congruent lithium niobate |year=1997 |pages=1553–1555 |doi=10.1364/OL.22.001553 |pmid=18188296 |issue=20 |bibcode=1997OptL...22.1553J}} gives

: $$

n^2_e \approx 5.35583 + 4.629 \times 10^{-7} f

+ \frac{0.100473 + 3.862 \times 10^{-8} f}{\lambda^2 - (0.20692 - 0.89 \times 10^{-8} f)^2}

+ \frac{100 + 2.657 \times 10^{-5} f}{\lambda^2 - 11.34927^2}

- 1.5334 \times 10^{-2} \lambda^2,

valid from 20 to 250 °C for wavelengths from 0.4 to 5 micrometers, whereas for longer wavelengths,{{cite journal |journal=Optics Communications |volume=268 |title=Improvement to Sellmeier equation for periodically poled LiNbO₃ crystal using mid-infrared difference-frequency generation |issue=1 |year=2006 |pages=110–114 |doi=10.1016/j.optcom.2006.06.082 |bibcode=2006OptCo.268..110D |last1=Deng |first1=L. H. |last2=Gao |first2=X. M. |last3=Cao |first3=Z. S. |last4=Chen |first4=W. D. |last5=Yuan |first5=Y.Q. |last6=Zhang |first6=W. J. |last7=Gong |first7=Z. B. }}

: $$

n^2_e \approx 5.39121 + 4.968 \times 10^{-7} f

+ \frac{0.100473 + 3.862 \times 10^{-8} f}{\lambda^2 - (0.20692 - 0.89 \times 10^{-8} f)^2}

+ \frac{100 + 2.657 \times 10^{-5} f}{\lambda^2 - 11.34927^2}

- (1.544 \times 10^{-2} + 9.62119 \times 10^{-10} \lambda) \lambda^2,

which is valid for T = 25 to 180 °C, for wavelengths λ between 2.8 and 4.8 micrometers.

In these equations f = (T − 24.5)(T + 570.82), λ is in micrometers, and T is in °C.

More generally for ordinary and extraordinary index for MgO-doped {{chem2|LiNbO3}}:

: $\{$

n^2 \approx a_1 + b_1 f

+ \frac{a_2 + b_2 f}{\lambda^2 - (a_3 + b_3 f)^2}

+ \frac{a_4 + b_4 f}{\lambda^2 - a_5^2}

- a_6 \lambda^2,

}

with:

for congruent {{chem2|LiNbO3}} (CLN) and stochiometric {{chem2|LiNbO3}} (SLN).{{cite journal |journal=Appl. Phys. B |volume=91 |issue=2 |title=Temperature and wavelength dependent refractive index equations for MgO-doped congruent and stoichiometric LiNbO₃ |year=2008 |pages=343–348 |doi=10.1007/s00340-008-2998-2 |bibcode=2008ApPhB..91..343G |s2cid=195290628 |last1=Gayer |first1=O. |last2=Sacks |first2=Z. |last3=Galun |first3=E. |last4=Arie |first4=A. }}

{{div col|colwidth=22em}}

• Crystal
• Crystal structure
• Crystallite
• Crystallization and engineering aspects
• Seed crystal
• Single crystal
• Laser-heated pedestal growth
• Micro-Pulling-Down
• Nickel niobate{{div col end}}

{{reflist|30em}}

• {{cite book |ref=Haynes| editor= Haynes, William M. | date = 2016| title = CRC Handbook of Chemistry and Physics | edition = 97th | publisher = CRC Press | isbn = 9781498754293 }}

• [https://web.archive.org/web/20040710120217/http://www.inrad.com/pdf/Inrad_datasheet_LNB.pdf Inrad data sheet on lithium niobate]

{{Lithium compounds}}

{{Niobium compounds}}

Category:Lithium salts

Category:Niobates

Category:Ferroelectric materials

Category:Nonlinear optical materials

Category:Crystals

Category:Second-harmonic generation