Editorial

3 pages, 175 KiB

Open AccessEditorial

by Robert A. Jackson and Zsuzsanna Szaller

Crystals 2020, 10(9), 780; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10090780 - 03 Sep 2020

Cited by 5 | Viewed by 1904

This special issue features eight papers which cover the recent developments in research on lithium niobate. Papers are divided into three groups based on their topic. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

Research

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11 pages, 2846 KiB

Open AccessArticle

Tunable Non-Volatile Memory by Conductive Ferroelectric Domain Walls in Lithium Niobate Thin Films

by Thomas Kämpfe, Bo Wang, Alexander Haußmann, Long-Qing Chen and Lukas M. Eng

Crystals 2020, 10(9), 804; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10090804 - 11 Sep 2020

Cited by 19 | Viewed by 3318

Abstract

Ferroelectric domain wall conductance is a rapidly growing field. Thin-film lithium niobate, as in lithium niobate on insulators (LNOI), appears to be an ideal template, which is tuned by the inclination of the domain wall. Thus, the precise tuning of domain wall inclination [...] Read more.

Ferroelectric domain wall conductance is a rapidly growing field. Thin-film lithium niobate, as in lithium niobate on insulators (LNOI), appears to be an ideal template, which is tuned by the inclination of the domain wall. Thus, the precise tuning of domain wall inclination with the applied voltage can be used in non-volatile memories, which store more than binary information. In this study, we present the realization of this concept for non-volatile memories. We obtain remarkably stable set voltages by the ferroelectric nature of the device as well as a very large increase in the conduction, by at least five orders of magnitude at room temperature. Furthermore, the device conductance can be reproducibly tuned over at least two orders of magnitude. The observed domain wall (DW) conductance tunability by the applied voltage can be correlated with phase-field simulated DW inclination evolution upon poling. Furthermore, evidence for polaron-based conduction is given. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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12 pages, 1675 KiB

Open AccessArticle

Computer Simulation of the Incorporation of V²⁺, V³⁺, V⁴⁺, V⁵⁺ and Mo³⁺, Mo⁴⁺, Mo⁵⁺, Mo⁶⁺ Dopants in LiNbO₃

by Romel Menezes Araujo, Emanuel Felipe dos Santos Mattos, Mário Ernesto Giroldo Valerio and Robert A. Jackson

Crystals 2020, 10(6), 457; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10060457 - 01 Jun 2020

Cited by 8 | Viewed by 2811

Abstract

The doping of LiNbO₃ with V²⁺, V³⁺, V⁴⁺ and V⁵⁺ as well as Mo³⁺, Mo⁴⁺, Mo⁵⁺ and Mo⁶⁺ ions is of interest in enhancing its photorefractive properties. In this paper, [...] Read more.

The doping of LiNbO₃ with V²⁺, V³⁺, V⁴⁺ and V⁵⁺ as well as Mo³⁺, Mo⁴⁺, Mo⁵⁺ and Mo⁶⁺ ions is of interest in enhancing its photorefractive properties. In this paper, possible incorporation mechanisms for these ions in LiNbO₃ are modelled, using a new set of interaction potentials fitted to the oxides VO, V₂O₃, VO₂, V₂O₅ and to LiMoO₂, Li₂MoO₃, LiMoO₃, Li₂MoO₄. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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9 pages, 1161 KiB

Open AccessArticle

Improvement on Thermal Stability of Nano-Domains in Lithium Niobate Thin Films

by Yuejian Jiao, Zhen Shao, Sanbing Li, Xiaojie Wang, Fang Bo, Jingjun Xu and Guoquan Zhang

Crystals 2020, 10(2), 74; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10020074 - 30 Jan 2020

Cited by 7 | Viewed by 3078

Abstract

We present a simple and effective way to improve the thermal stability of nano-domains written with an atomic force microscope (AFM)-tip voltage in a lithium niobate film on insulator (LNOI). We show that nano-domains in LNOI (whether in the form of stripe domains [...] Read more.

We present a simple and effective way to improve the thermal stability of nano-domains written with an atomic force microscope (AFM)-tip voltage in a lithium niobate film on insulator (LNOI). We show that nano-domains in LNOI (whether in the form of stripe domains or dot domains) degraded, or even disappeared, after a post-poling thermal annealing treatment at a temperature on the order of ∼100

^{\circ}

C. We experimentally confirmed that the thermal stability of nano-domains in LNOI is greatly improved if a pre-heat treatment is carried out for LNOI before the nano-domains are written. This thermal stability improvement of nano-domains is mainly attributed to the generation of a compensating space charge field parallel to the spontaneous polarization of written nano-domains during the pre-heat treatment process. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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9 pages, 1860 KiB

Open AccessArticle

High Homogeneity of Magnesium Doped LiNbO₃ Crystals Grown by Bridgman Method

by Xiaodong Yan, Tian Tian, Menghui Wang, Hui Shen, Ding Zhou, Yan Zhang and Jiayue Xu

Crystals 2020, 10(2), 71; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10020071 - 29 Jan 2020

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Abstract

A series of LiNbO₃ crystals doped with various MgO concentrations (0, 3%, and 5 mol%) was simultaneously grown in one furnace by the modified vertical Bridgman method. The wet chemistry method was used to prepare the polycrystalline powders, and the growth conditions [...] Read more.

A series of LiNbO₃ crystals doped with various MgO concentrations (0, 3%, and 5 mol%) was simultaneously grown in one furnace by the modified vertical Bridgman method. The wet chemistry method was used to prepare the polycrystalline powders, and the growth conditions were optimized. The full width at half maximum of high-resolution X-ray rocking curves for (001) reflection of 5 mol% Mg doped lithium niobate (LN) crystal was about 8″, which meant it possessed high crystalline quality. The OH⁻ absorption spectra shifted to 3534.7 cm⁻¹, and the UV absorption edge violet shift indicated that 5 mol% MgO successfully doped in LN and exceeded the threshold. The extraordinary refractive index gradient of 5 mol% Mg doped LN crystal was as small as 2.5 × 10⁻⁵/cm, which exhibited high optical homogeneity. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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8 pages, 2852 KiB

Open AccessArticle

Design and Optimization of Proton Exchanged Integrated Electro-Optic Modulators in X-Cut Lithium Niobate Thin Film

by Huangpu Han, Bingxi Xiang, Tao Lin, Guangyue Chai and Shuangchen Ruan

Crystals 2019, 9(11), 549; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9110549 - 24 Oct 2019

Cited by 10 | Viewed by 4215

Abstract

In this study, we designed, simulated, and optimized proton exchanged integrated Mach-Zehnder modulators in a 0.5-μm-thick x-cut lithium niobate thin film. The single-mode conditions, the mode distributions, and the optical power distribution of the lithium niobate channel waveguides are discussed and compared in [...] Read more.

In this study, we designed, simulated, and optimized proton exchanged integrated Mach-Zehnder modulators in a 0.5-μm-thick x-cut lithium niobate thin film. The single-mode conditions, the mode distributions, and the optical power distribution of the lithium niobate channel waveguides are discussed and compared in this study. The design parameters of the Y-branch and the separation distances between the electrodes were optimized. The relationship between the half-wave voltage length production of the electro-optic modulators and the thickness of the proton exchanged region was studied. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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11 pages, 3995 KiB

Open AccessArticle

An Integrated Photonic Electric-Field Sensor Utilizing a 1 × 2 YBB Mach-Zehnder Interferometric Modulator with a Titanium-Diffused Lithium Niobate Waveguide and a Dipole Patch Antenna

by Hongsik Jung

Crystals 2019, 9(9), 459; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9090459 - 02 Sep 2019

Cited by 14 | Viewed by 3868

Abstract

We studied photonic electric-field sensors using a 1 × 2 YBB-MZI modulator composed of two complementary outputs and a 3 dB directional coupler based on the electro-optic effect and titanium diffused lithium–niobate optical waveguides. The measured DC switching voltage and extinction ratio at [...] Read more.

We studied photonic electric-field sensors using a 1 × 2 YBB-MZI modulator composed of two complementary outputs and a 3 dB directional coupler based on the electro-optic effect and titanium diffused lithium–niobate optical waveguides. The measured DC switching voltage and extinction ratio at the wavelength 1.3 μm were ~16.6 V and ~14.7 dB, respectively. The minimum detectable fields were ~1.12 V/m and ~3.3 V/m, corresponding to the ~22 dB and ~18 dB dynamic ranges of ~10 MHz and 50 MHz, respectively, for an rf power of 20 dBm. The sensor shows an almost linear response to the applied electric-field strength within the range of 0.29 V/m to 29.8 V/m. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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18 pages, 5103 KiB

Open AccessArticle

Determination of the Chemical Composition of Lithium Niobate Powders

by Oswaldo Sánchez-Dena, Carlos J. Villagómez, César D. Fierro-Ruíz, Artemio S. Padilla-Robles, Rurik Farías, Enrique Vigueras-Santiago, Susana Hernández-López and Jorge-Alejandro Reyes-Esqueda

Crystals 2019, 9(7), 340; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9070340 - 03 Jul 2019

Cited by 11 | Viewed by 4722

Abstract

Existent methods for determining the composition of lithium niobate single crystals are mainly based on their variations due to changes in their electronic structure, which accounts for the fact that most of these methods rely on experimental techniques using light as the probe. [...] Read more.

Existent methods for determining the composition of lithium niobate single crystals are mainly based on their variations due to changes in their electronic structure, which accounts for the fact that most of these methods rely on experimental techniques using light as the probe. Nevertheless, these methods used for single crystals fail in accurately predicting the chemical composition of lithium niobate powders due to strong scattering effects and randomness. In this work, an innovative method for determining the chemical composition of lithium niobate powders, based mainly on the probing of secondary thermodynamic phases by X-ray diffraction analysis and structure refinement, is employed. Its validation is supported by the characterization of several samples synthesized by the standard and inexpensive method of mechanosynthesis. Furthermore, new linear equations are proposed to accurately describe and determine the chemical composition of this type of powdered material. The composition can now be determined by using any of four standard characterization techniques: X-Ray Diffraction (XRD), Raman Spectroscopy (RS), UV-vis Diffuse Reflectance (DR), and Differential Thermal Analysis (DTA). In the case of the existence of a previous equivalent description for single crystals, a brief analysis of the literature is made. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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15 pages, 2947 KiB

Open AccessArticle

Mechanochemical Reactions of Lithium Niobate Induced by High-Energy Ball-Milling

by Laura Kocsor, László Péter, Gábor Corradi, Zsolt Kis, Jenő Gubicza and László Kovács

Crystals 2019, 9(7), 334; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9070334 - 28 Jun 2019

Cited by 16 | Viewed by 3036

Abstract

Lithium niobate (LiNbO₃, LN) nanocrystals were prepared by ball-milling of the crucible residue of a Czochralski grown congruent single crystal, using a Spex 8000 Mixer Mill with different types of vials (stainless steel, alumina, tungsten carbide) and various milling parameters. Dynamic [...] Read more.

Lithium niobate (LiNbO₃, LN) nanocrystals were prepared by ball-milling of the crucible residue of a Czochralski grown congruent single crystal, using a Spex 8000 Mixer Mill with different types of vials (stainless steel, alumina, tungsten carbide) and various milling parameters. Dynamic light scattering and powder X-ray diffraction were used to determine the achieved particle and grain sizes, respectively. Possible contamination from the vials was checked by energy-dispersive X-ray spectroscopy measurements. Milling resulted in sample darkening due to mechanochemical reduction of Nb (V) via polaron and bipolaron formation, oxygen release and Li₂O segregation, while subsequent oxidizing heat-treatments recovered the white color with the evaporation of Li₂O and crystallization of a LiNb₃O₈ phase instead. The phase transformations occurring during both the grinding and the post-grinding heat treatments were studied by Raman spectroscopy, X-ray diffraction and optical reflection measurement, while the Li₂O content of the as-ground samples was quantitatively measured by coulometric titration. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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8 pages, 4840 KiB

Open AccessArticle

The Photorefractive Response of Zn and Mo Codoped LiNbO₃ in the Visible Region

by Liyun Xue, Hongde Liu, Dahuai Zheng, Shahzad Saeed, Xuying Wang, Tian Tian, Ling Zhu, Yongfa Kong, Shiguo Liu, Shaolin Chen, Ling Zhang and Jingjun Xu

Crystals 2019, 9(5), 228; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9050228 - 28 Apr 2019

Cited by 8 | Viewed by 2353

Abstract

We mainly investigated the effect of the valence state of photorefractive resistant elements on the photorefractive properties of codoped crystals, taking the Zn and Mo codoped LiNbO₃ (LN:Mo,Zn) crystal as an example. Especially, the response time and photorefractive sensitivity of 7.2 mol% [...] Read more.

We mainly investigated the effect of the valence state of photorefractive resistant elements on the photorefractive properties of codoped crystals, taking the Zn and Mo codoped LiNbO₃ (LN:Mo,Zn) crystal as an example. Especially, the response time and photorefractive sensitivity of 7.2 mol% Zn and 0.5 mol% Mo codoped with LiNbO₃ (LN:Mo,Zn_7.2) crystal are 0.65 s and 4.35 cm/J at 442 nm, respectively. The photorefractive properties of the LN:Mo,Zn crystal are similar to the Mg and Mo codoped LiNbO₃ crystal, which are better than the Zr and Mo codoped LiNbO₃ crystal. The results show that the valence state of photorefractive resistant ions is an important factor for the photorefractive properties of codoped crystals and that the LN:Mo,Zn_7.2 crystal is another potential material with fast response to holographic storage. Full article

(This article belongs to the Special Issue Recent Progress in Lithium Niobate)

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