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Spectra (UV-Visible, IR transmission) of Sc3+, Fe3+ and Cu2+ tri-doped LiNbO <sub/>3</sub> crystals with various [Li]/[Nb] ratios
摘要： The Sc:Fe:Cu:LiNbO3 crystals were grown with Fe3+(0.3 wt.%), Cu2+(0.1 wt.%) and Sc3+(1 mol.%) by the Czochralski method with various [Li]/[Nb] ratios (0.946, 1.05, 1.20 and 1.38). The influence of the [Li]/[Nb] ratios on the defect structure of Sc:Fe:Cu:LiNbO3 crystals was analyzed by the UV-Visible spectra and IR transmission spectra. The spectra show that the absorption edge shift to the red with [Li]/[Nb] ratios enhancing. The Sc:Fe:Cu:LiNbO3 crystals with [Li]/[Nb] ratio of 1.05 is nearly stoichiometric. A new narrow OH- associated vibrational peak at 3505 cm-1 was revealed in Sc:Fe:Cu:LiNbO3 crystals with the ratio of [Li]/[Nb] = 1.38. It is attributed to the (Sc2-Nb)-(OH)-. The results show that the defect structure changes with the [Li]/[Nb] ratios variation.
关键词： IR transmission spectrum,Sc:Fe:Cu:LiNbO3 crystal,UV-Visible spectrum
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - SH-Type Spurious Response Free TC-SAW Resonators Using Low Acoustic Velocity Rayleigh SAW on LiNbO<inf>3</inf> Substrate
摘要： In this paper, we describe the behavior of the spurios resonance caused by shear-horizontal (SH) type surface acoustic wave (SAW) devices in low acoustic velocity (LAV) Rayleigh-type SAW structures. It is well known that an SH-type SAW or Rayleigh-type SAW device appears near the main resonance on LiNbO3 (LN) substrates, which causes various undesired effects on the device characteristics. However, they are often non-negligible in practical use. In order to explore a solution of this problem, we theoretically and experimentally investigated the variation of the SH-type SAW resonance in the low acoustic velocity (LAV) Rayleigh-type SAW structure on LN substrates, which is a new LAV-SAW structure with a higher performance temperature-compensated (TC) SAW device (TC-SAW) technology. As a result, we revealed that the SH-type SAW can be almost zero even if various parameters are changed. Moreover, very small sized and TC-SAW devices can be realized using this new technology.
关键词： temperature compensation,SAW,Rayleigh-type SAW,acoustic velocity,LiNbO3,SH-type SAW
更新于2025-09-23 15:22:29
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Ferroelectric Polarization Rotation in Order-Disorder-Type LiNbO3 Thin Films
摘要： The direction of ferroelectric polarization is prescribed by the symmetry of the crystal structure. Therefore, rotation of the polarization direction is largely limited, despite the opportunity it offers in understanding important dielectric phenomena such as piezoelectric response near the morphotropic phase boundaries and practical applications such as ferroelectric memory. In this study, we report the observation of continuous rotation of ferroelectric polarization in order-disorder-type LiNbO3 thin films. The spontaneous polarization could be tilted from an out-of-plane to an in-plane direction in the thin film by controlling the Li vacancy concentration within the hexagonal lattice framework. Partial inclusion of monoclinic-like phase is attributed to the breaking of macroscopic inversion symmetry along different directions and the emergence of ferroelectric polarization along the in-plane direction.
关键词： second harmonic generation,vacancy engineering,spatial inversion symmetry breaking,ferroelectric polarization rotation,LiNbO3 thin films
更新于2025-09-23 15:21:21
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Study of materials structure physics of isomorphic LiNbO <sub/>3</sub> and LiTaO <sub/>3</sub> ferroelectrics by synchrotron radiation X-ray diffraction
摘要： Electron charge density studies of stoichiometric LiNbO3 and LiTaO3 ferroelectrics have been carried out by analyzing the synchrotron radiation X-ray powder di?raction data using a combination of the Rietveld and maximum entropy methods. The clear relationships between the Nb(Ta)–O bond length, the electron charge density on the Nb(Ta)–O bond, and the phase transition temperature TC are revealed for isomorphic structures. Nb(Ta)–O bonding plays an important role in the elevation of TC. The TC in LiNbO3 being higher than that in LiTaO3 is attributed to the larger lattice distortion of the Nb–O oxygen octahedron in LiNbO3. The validity of estimating TC for LiNbO3 family crystals from the degree of lattice distortion in the ferroelectric structure is discussed.
关键词： ferroelectric,LiTaO3,X-ray diffraction,synchrotron radiation,LiNbO3,phase transition temperature,electron charge density
更新于2025-09-23 15:21:21
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Simultaneous generation of two THz waves with bulk LiNbO3 and four THz waves with PPLN by coupled optical parametric generation
摘要： We present a theoretical research concerning simultaneous generation of two terahertz (THz) waves with bulk LiNbO3 and four THz waves with periodically poled LiNbO3 (PPLN) by coupled optical parametric generation (COPG). First, we investigate collinear phase matching of COPG generating two orthogonally polarized THz waves with two types of phase matching of o = e ? e and o = e ? o with bulk LiNbO3. The two orthogonally polarized THz waves are generated from stimulated polariton scattering (SPS) with A1 and E symmetric transverse optical (TO) modes in bulk LiNbO3, respectively. Then, we ?nd that perturbations of phase mismatch for o = e ? e and o = e ? o can be compensated by a same grating vector of PPLN. As a result, four THz waves are simultaneously generated with a PPLN crystal and a pump laser. We calculate third-order nonlinear optical coef?cients of o = e ? o generating THz waves from E symmetric TO modes. The intensities of four THz waves are calculated by solving coupled-wave equations. The calculation results demonstrate that four THz waves with high intensities can be simultaneously realized by COPG with existing laser technology and crystal fabrication technology.
关键词： Stimulated polariton scattering,Coupled optical parametric generation,Periodically poled LiNbO3,Terahertz wave
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Conference on Antenna Measurements & Applications (CAMA) - Kuta, Bali, Indonesia (2019.10.23-2019.10.25)] 2019 IEEE Conference on Antenna Measurements & Applications (CAMA) - Receiving Performance of Antenna-Coupled Electrode Electro-Optic Modulators for 5G Frequency Band
摘要： We have already proposed and developed an antenna-coupled- electrode electro-optic (EO) modulator for 28 GHz-band 5th generation mobile communication as a receiving antenna. The designed EO modulator was fabricated a metal ground plane backed linear dipole array using a 50-μm-thick LiNbO3 crystal and a 250-μm-thick SiO2 base. In this paper, we have shown antenna receiving patterns for 1-element dipole antenna, 4-element dipole array antenna and 8-elemen dipole array antenna. Half power beam width for H-plane of our developed receiving antennas are 70, 25 and 11 degree for 1 element, 4-element and 8-element dipole array, respectively.
关键词： 5G mobile communication,radio over fiber,LiNbO3,optical modulator,receiving antenna,ground plane backed dipole array
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Periodically Poled MgO:LiNbO <sub/>3</sub> , MgO:LiTaO <sub/>3</sub> and KTiOPO <sub/>4</sub> Crystals for Laser Light Frequency Conversion
摘要： We present the recent achievements in periodical poling in MgO doped single crystals of lithium niobate (LN), lithium tantalate (LT) and potassium titanyl phosphate (KTP) based on the experimental study of the domain structure evolution by the complementary high-resolution domain visualization methods [1]. The crystals with tailored periodically poled domain structures (PPLN and PPLT) produced with nano-scale period reproducibility have been used for Second Harmonic Generation (SHG) and Optical Parametric Oscillation (OPO) based on quasi-phase-matched nonlinear optical wavelength conversion. The periodical poling techniques were based on the deep experimental and theoretical study of the mechanisms of domain growth and domain wall motion in these crystals. The wide range of wall velocities with two orders of magnitude difference was observed for switching in a uniform electric field [2,3]. The kinetic maps allowed analyzing the spatial distribution of the wall motion velocities and classifying the walls by velocity ranges. The distinguished slow, fast, and superfast types of domain walls in KTP differed by their orientation. The revealed increase in the wall velocity with deviation from low-index crystallographic planes for slow and fast walls was considered in terms of determined step generation and anisotropic kink motion. It was shown that the polarization reversal in KTP with artificial surface dielectric layer leads to formation and growth of the large number of narrow domain streamers oriented strictly along [010] direction with about ten times higher velocity (6-60 mm/s) than the domain walls (2-5.5 mm/s). Study of the static domain structures demonstrated that the streamers are formed by [100] and [010]-oriented domain walls. The streamer width was about 500 nm and the distance between the neighboring streamers – about 100 nm. The global domain kinetics during the poling process at elevated temperatures has been studied by in situ optical observation which allowed us to reveal the main characteristics of the poling process at elevated temperatures. It has been shown that the periodically poled area propagates from the edges to the middle of the electrode pattern. The interfering effect of essential increasing of the bulk conductivity during poling has been studied and several ways to overcome this problem have been proposed. The static domain images revealed by chemical etching were visualized by optical and scanning probe microscopy. The influence of the spatially nonuniform electric field on the domain kinetics has been studied for finite-size electrodes of various shapes. The key role of the field anomalies at the electrode corners, ends, and edges in the nucleation process has been revealed by computer simulations and confirmed experimentally. Essential acceleration of the switching at the boundaries of the electrode patterns (so called “pattern effect”) has been explained. The optimized design of the electrode pattern was based on experimental results and computer simulation. The fan-out periodical domain structures created in 3-mm-thick MgO:LN wafers allowed us to realize the widely tunable OPO generation with the signal wave from 2.5 to 4.5 μm using the 1.053 μm pump. The possibility of producing the elements with thickness up to 10 mm for high-power application has been discussed. The peridical domain struture with period of 40 μm was created in KTP single crystals for OPO generation at 2.4 μm using the 1.053 μm pump. The abilities and perspectives of producing the elements with submicron periods has been discussed. The optimized periodical poling techniques have been used for creation of ridge waveguides in periodically poled MgOLN single crystals. The high-index contrast of obtained multi-mode waveguides allowed tuning of the SHG wavelength from 510 to 570 nm using the 1.064 μm pump. The deep knowledge of the domain structure evolution at elevated temperatures and relaxation of the high bulk conductivity along the charged domain walls MgO:LN and MgO:LT allowed us to optimize the periodical poling technique and to produce high-fidelity domain patterns.
关键词： domain structure evolution,MgO:LiTaO3,KTiOPO4,Second Harmonic Generation,Optical Parametric Oscillation,MgO:LiNbO3,Periodically Poled
更新于2025-09-23 15:19:57
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Enhancement of the second harmonic signal of nonlinear crystals by self-assembled gold nanoparticles
摘要： In second harmonic generation (SHG), the energy of two incoming photons, e.g., from a femtosecond laser, can be combined in one outgoing photon of twice the energy, e.g., by means of a nonlinear crystal. The SHG efficiency, however, is limited. In this work, the harvested signal is maximized by composing a hybrid system consisting of a nonlinear crystal with a dense coverage of plasmonic nanostructures separated by narrow gaps. The method of self-assembled diblock-copolymer-based micellar lithography with subsequent electroless deposition is employed to cover the whole surface of a lithium niobate (LiNbO3) crystal. The interaction of plasmonic nanostructures with light leads to a strong electric near-field in the adjacent crystal. This near-field is harnessed to enhance the near-surface SHG signal from the nonlinear crystal. At the plasmon resonance of the gold nanoparticles, a pronounced enhancement of about 60-fold SHG is observed compared to the bare crystal within the confocal volume of a laser spot.
关键词： gold nanoparticles,nonlinear crystal,second harmonic generation,lithium niobate,plasmonic nanostructures,electroless deposition,self-assembled diblock-copolymer-based micellar lithography,LiNbO3,SHG
更新于2025-09-23 15:19:57
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Hf <sup>?4+</sup> Ion Concentration Dependence of Holographic Storage Properties in Hf:Fe:Cu:LiNbO <sub/>3</sub> Crystals
摘要： A series of Hf:Fe:Cu:LiNbO3 crystal with various concentrations of Hf 4+ ion doping are grown in air by the conventional Czochralski technique. The segregation coe?cients of the Hf 4+, Fe3+, and Cu2+ ions in the crystals are carried out with an inductively coupled plasma-atomic emission spectrometer. The birefringence gradient method is measured in order to analyze the optical homogeneity of Hf:Fe:Cu:LiNbO3 crystals. The holographic storage properties of Hf:Fe:Cu:LiNbO3 crystals are investigated by the two-wavelength coupling experiment. The result shows that the writing time constant shortens from 529.3 to 214.4 s, and the dynamic range increases from 1.12 to 8.07 with increasing Hf 4+ content in the Hf:Fe:Cu:LiNbO3 crystals.
关键词： holographic storage,Hf:Fe:Cu:LiNbO3 crystal,segregation coe?cients
更新于2025-09-23 15:19:57
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Interaction between Bi Dopants and Intrinsic Defects in LiNbO <sub/>3</sub> from Local and Hybrid Density Functional Theory Calculations
摘要： The interactions between Bi dopants including Bi-substituting Li (BiLi) and Bi-substituting Nb (BiNb) and the intrinsic antisite defects (NbLi) and Li vacancies (VLi) in LiNbO3 are investigated using local and hybrid density functional theories. Three charge-compensated defect clusters, BiLi4+ + NbLi4+ + 8VLi-, BiLi4+ + 4VLi-, and BiLi0 + 4VLi- + BiNb4+, are modeled in this work to investigate the effects of the Bi concentration. The most stable cluster configurations, the Bi-doping stability in the clusters, and the electronic state interaction between Bi and intrinsic defects have been studied in detail. It is found that BiLi4+ has a stronger electron-capturing ability than NbLi4+ in Bi-doped congruent LiNbO3. The BiLi-doping-induced local lattice distortion and the electron-trapping behavior remain unchanged with increasing Bi-doping concentration. However, the position of the Bi defect states in the band gap is found to be shifted in congruent LiNbO3. This is mainly attributed to the large lattice relaxation induced by the large number of Li vacancies instead of the ionic level redistribution caused by the direct interaction between Bi and intrinsic defects.
关键词： LiNbO3,Bi dopants,lattice distortion,defect clusters,intrinsic defects,density functional theory,electron trapping
更新于2025-09-19 17:15:36