Periodic Domain Structure Research Articles

Formation of photon ferroelectric crystals with the use of quasi-standing acoustic waves

An acoustic-interference method of formation of photon ferroelectric crystals is investigated. The method does not necessitate photolithography. Schemes of formation of periodic domain structures with the use of elastic waves that interfere in the ferroelectric volume are considered. It is shown that this technology is the most efficient for the creation of photon crystals based on high-coercitivity ferroelectrics, for example, pure congruent-composition LiNbO3.

Structure and Metal‐to‐Insulator Transition of VO2 Nanowires Grown on Sapphire Substrates

AbstractSingle‐crystalline VO2 nanowires exhibit interesting growth phenomena along three equivalent <1$\bar {1}$00> directions of the C‐planes of the sapphire substrates. Under certain growth conditions, VO2 nanowires form V‐shaped twining structures with uniform morphologies and interfaces. Due to the strong elastic stress at the interfaces, the metal‐to‐insulator transition (MIT) of individual VO2 nanowires grown directly on sapphire substrates were observed to display distinct electrical hysteresis loops relative to VO2 nanowires dispersed on sapphire substrates. The distinctive characteristics in the hysteresis loops, exhibited in the process of MIT, are shown to be correlated with the nucleation and growth of periodic/random domain structures in the nanowires during the heating and cooling processes. The periodic domain structures observed in the directly grown nanowires can be explained under the framework of a modified stress‐induced elastic energy model that was first developed for ferroelectric systems.

Periodic domain structures formed under electron-beam irradiation in LiNbO3 plates and Ti:LiNbO3 planar waveguides of the Y cut

Regular domain structures on the Y cuts of the LiNbO3 substrates and Ti:LiNbO3 waveguide structures based on these substrates have been fabricated under electron-beam irradiation. It has been revealed that the domains in undoped and titanium-doped LiNbO3 crystals are formed as a result of different processes. It has been demonstrated using chemical etching and waveguide second-harmonic generation that regular domain structures in the Ti:LiNbO3 waveguides are formed at a depth of approximately 8 μm from the surface, where the titanium concentration does not exceed 2 mol %. The quasi-synchronous waveguide optical second harmonic generation with an efficiency of 8.8% has been obtained using the fabricated structures.

Investigation of Periodic Domain Structures in LiNbO3:Gd Single Crystals

This work discusses the results of investigations of the growth of periodic domain structure in gadolinium-doped LiNbO3 crystals using scanning electron and atomic-force microscopy (SEM and AFM). Comparative analysis of “head-to-head” and “tail-to-tail” domain walls allows us to reveal their difference in shape and physical properties. It was revealed by AFM in the lateral force mode and by SEM charging technique that the charging of the crystal surface near the “tail-to-tail” walls during electron bombardment occured slower and the same surface areas had altered elastic surface properties. It was supposed that observed morphological and physical peculiarities were caused by difference in gradients of Gd concentration and their spatial distribution near domain walls of different types.

Optical Investigations of Periodical Domain Structures Created by E-Beam Irradiation in Y-Cut LiNbO3

We report the results of optical investigations of planar periodical domain structures fabricated by a set of quasi-point e-beam irradiations both on a Y-cut congruent LiNbO3 substrate and on the planar Ti-indiffused waveguides that have been formed on such substrates. The quasi-phase-matched second harmonic generation (SHG) on domain gratings with period of 7 μm has been obtained with the conversion efficiency 8.8%. A quality of the planar domain gratings was estimated by SHG-microscopy and light scattering.

Raman visualization of micro- and nanoscale domain structures in lithium niobate

In this work we demonstrate the abilities of micro-Raman imaging in the study of ferroelectric domains and present its application to visualization of micro-scale periodical domain structures and nano-domains induced by laser irradiation in lithium niobate.

Origin of periodic domain structure in Er 3+-doped β′-(Sm,Gd) 2(MoO 4) 3 crystal lines patterned by laser irradiations in glasses

Er 3+-doped β′-(Sm,Gd) 2(MoO 4) 3 crystal lines are patterned on the surface of Er 2O 3–Gd 2O 3–Sm 2O 3–MoO 3–B 2O 3 glasses by continuous-wave Yb:YVO 4 laser irradiations (wavelength: 1080 nm, power: 1.3 W, scanning speeds: 5 μm/s), and the origin of the periodicity of self-organized domain structures with high and low refractive index regions in crystal lines is examined from polarized optical microscope (POM) observations, micro-Raman scattering spectrum, and photoluminescence spectrum measurements. It is found that the periodicity of domain structures changes largely depending on Er 2O 3 content, i.e., the length of high (bright color in POM observations) and low (dark color) refractive index regions increases with increasing Er 2O 3 content and homogeneous crystal lines with no periodic domain structures are patterned in Er 2O 3–Sm 2O 3–MoO 3–B 2O 3 glass with no Gd 2O 3. Considering that the degree of ferroelasticities in β′-(Sm,Gd) 2(MoO 4) 3 crystals decreases due to the incorporation of Er 3+ ions, it is demonstrated that the origin of periodic domain structures in laser-patterned lines is due to spontaneous strains in ferroelastic β′-(Sm,Gd) 2(MoO 4) 3 crystals.

Effect of defects of the domain structure on the optical properties of ferroelectric crystals

The effect of irregularities of a periodic domain structure on the efficiency of the second harmonic generation has been numerically investigated in the case where the structure is formed by the high-voltage method. The irregularities associated with the uncontrollable motion of domain walls from under electrodes, as well as with the presence of internal defects in the crystal, have been analyzed.

Difference frequency generation by optical rectification of femtosecond laser pulse in GaAs crystal with a periodic domain structure

We study the influence of spatial boundedness of a femtosecond laser pulse (FLP) on the efficiency of generation of difference frequency radiation (DFR) in a GaAs crystal with a periodic domain structure. It is shown that at propagation of DFR a spectral-angular filtration occurs in the transverse distribution of the beam. An expression is obtained for the frequency-angular spectrum of DFR. For a pump pulse with the duration of 100 fs, the beam radius of 24μm, the energy of 30 nJ, and the wavelength of 1.98μm propagating in 1.716-mm long GaAs crystal with the domain structure period of 74.6μm the efficiency of generation of DFR at the wavelength of 14μm is calculated to be close to 2×10−6.

10.1007/s11451-008-3008-6

The photonic-crystal properties of a magnetically gyrotropic medium having a periodic planar layered domain structure are studied. The magnetic gyrotropy of the medium in the optical range is revealed in the permittivity tensor. The dispersion relation of the TM wave controlled by an external magnetic field is obtained and analyzed both in the fine-layered medium approximation and in the case where the ω(k) spectrum contains allowed bands and bandgaps in the wavenumber range under study. The effect of the symmetry of the structure on its spectrum is studied.

Two-dimensional Raman imaging for periodic domain structures in laser-patterned ferroelastic β′-(Sm,Gd)2(MoO4)3 crystal lines in glass

Abstract Ferroelastic β′-(Sm,Gd)2(MoO4)3, (SGMO), crystal lines are patterned on the surface of Sm2O3–Gd2O3–MoO3–B2O3 glasses by continuous-wave Yb:YVO4 laser irradiations (wavelength: 1080 nm, power: 1.2 W, scanning speeds: 4–7 μm/s), and the structure of periodic domains self-organized in the crystal lines is examined from two-dimensional micro-Raman scattering spectrum imaging. It is found that the periodicity in the domain structures with different refractive indices changes depending on the laser scanning speed, i.e., on the growth rate of SGMO crystals. It is proposed that the arrangements of (MoO4)2− tetrahedra giving the antisymmetric Mo–O stretching vibrations in SGMO crystals changes along the crystal growth direction (i.e., along the line) gradually and periodically due to spontaneous strains. The present study suggests that the appearance of periodic domain structures and second harmonic intensities is an intrinsic feature in the laser patterning of ferroelastic β′-(Sm,Gd)2(MoO4)3 crystals.

Imaging of Ferroelectric Micro-Domains in X-Cut Lithium Niobate by Confocal Second Harmonic Microscopy

We present results on ferroelectric micro-domains obtained by confocal second harmonic microscopy. The high potential of this technique is demonstrated by imaging periodic ferroelectric domain structures in the surface of planar X-cut lithium niobate (LN) and in the body of ridges fabricated by plasma etching on X-cut LN as well. In both cases the measured second harmonic signal reveals a strong contrast between inverted and non-inverted domain sections. This enabled a depth-resolved non-destructive tomography of micro-domains in ridge structures in all three dimensions.

Field-induced light deflection in lithium niobate and lithium tantalate: the possible configurations

Field-induced light deflection by ferroelectric domain walls in lithium niobate (LN) and lithium tantalate (LT) is theoretically studied. The phenomenon can occur not only when both the incident wave vector k and the electric field E are parallel to the z-axis—as demonstrated by experiments made so far—but also when E and/or k are perpendicular to z. In particular, for E parallel to x and k parallel to y, the deflection phenomenon is predicted to have the same characteristics as in triclinic or monoclinic ferroelastics: the large deflection angle is related to the natural birefringence, whereas the deflection amplitude is proportional to the small tilt angle of the neutral lines, which is here induced by the electric field. In periodic domain structures, interference between deflected waves occurs, and the deflected intensity is expected to be largely enhanced when the Bragg condition is satisfied. This transverse configuration is thus specially attractive to characterize periodically-poled crystals.

Autoresonance excitation of oscillations of domain walls in a ferromagnetic film

Nonlinear oscillations of domain walls in a ferromagnetic film with a plane-parallel periodic domain structure have been studied analytically and numerically in an external field with slowly changing amplitude and frequency. The conditions for the controlled autoresonance excitation of nonlinear oscillations of a domain wall in the presence of dissipation have been determined. The threshold values of the amplitude and rate of amplitude growth of the field of pumping have been found depending on the geometrical characteristics of the domain structure of the films whose exceeding generates an effect of autophasing in the system. It is shown that the magnetic saturation of a ferromagnetic film in the autoresonance regime can occur in fields that are substantially less than the fields of dynamic stationary magnetization.

Ferromagnetic resonance in a plate with a stripe domain structure with allowance for the inhomogeneity of the demagnetizing field

A numerical simulation of ferromagnetic resonance (FMR) in the absence of an external magnetic field has been performed for a plate with a high quality factor. A domain structure with Bloch domain walls (DWs) has been studied. It has been shown that the allowance for the inhomogeneity of the intrinsic demagnetizing field leads to the appearance of additional peaks in the FMR spectrum. With decreasing plate thickness, there occurs a displacement of the resonance-curve peaks into the region the low frequencies. An increase in the size of one of the domains at the expense of another in the periodic domain structure leads to an increase in the amplitude of the susceptibility of the low-frequency FMR mode and its shift into the region of low frequencies. Accordingly, the amplitude of the susceptibility of the high-frequency mode decreases and is shifted into the region of high frequencies. Furthermore, in the presence of resonance, in the plate with unequal domains the peak of the resonance curve that corresponds to the high-frequency mode is observed also upon the excitation of oscillations by an external ac field perpendicular to the DW, and the peak corresponding to the low-frequency mode, upon the excitation by an ac field parallel to the DW. These features of the FMR are explained by the corresponding changes in the inhomogeneous demagnetizing field.

Self-powdering and nonlinear optical domain structures in ferroelastic β′-Gd 2(MoO 4) 3 crystals formed in glass

Ferroelastic β′-Gd 2(MoO 4) 3, (GMO), crystals are formed through the crystallization of 21.25Gd 2O 3–63.75MoO 3–15B 2O 3 glass (mol%), and two scientific curious phenomena are observed. (1) GMO crystals formed in the crystallization break into small pieces with a triangular prism or pyramid shape having a length of 50–500 μm spontaneously during the crystallizations in the inside of an electric furnace, not during the cooling in air after the crystallization. This phenomenon is called “self-powdering phenomenon during crystallization” in this paper. (2) Each self-powdered GMO crystal grain shows a periodic domain structure with different refractive indices, and a spatially periodic second harmonic generation (SHG) depending on the domain structure is observed. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of second harmonic intensities that GMO crystals are oriented in each crystal grain and the orientation of (MoO 4) 2− tetrahedra in GMO crystals changes periodically due to spontaneous strains in ferroelastic GMO crystals.

Concentration dependence of the coherent contribution from domain walls to electrical resistance

The contribution from the Levy-Zhang mechanism to the magnetoresistance of a stripe domain structure is analyzed, and the dependence of this contribution on the domain wall concentration is found for the cases where the characteristic spin-diffusion length either exceeds or is far less than the domain structure period.

Radiation-damage-assisted ferroelectric domain structuring in magnesium-doped lithium niobate

Irradiation of 5% magnesium-doped lithium niobate crystals (LiNbO3:Mg) with high-energy, low-mass 3He ions, which are transmitted through the crystal, changes the domain reversal properties of the material. This enables easier domain engineering compared to non-irradiated material and assists the formation of small-sized periodically poled domains in LiNbO3:Mg. Periodic domain structures exhibiting a width of ≈520 nm are obtained in radiation-damaged sections of the crystals. The ferroelectric poling behavior between irradiated and non-treated material is compared.

The Spectrum of Magnetostatic Waves in Ferromagnetic with Moving Periodical Domain Structure

The spectral properties of magnetostatic waves in a ferromagnet with a moving periodic domain structure are studied within the exchange-free magnetostatic approximation. It is demonstrated that the Doppler frequency shift caused by the domain-wall motion results in the splitting of the spectrum of each magnetostatic wave mode into two dispersion branches―high-frequency and low-frequency branches. It is found that the more the mode number, the more the separation between these branches with respect to the mode spectrum in the presence of the static domain structure. PACS numbers: 75.60.-d, 75.60.Ch, 75.70.Kw

Corrected Article: “Self-organized periodic domain structure for second harmonic generations in ferroelastic β′-(Sm,Gd)2(MoO4)3 crystal lines on glass surfaces” [Appl. Phys. Lett. 94, 041915 (2009)

Ferroelastic β′-(Sm,Gd)2(MoO4)3 (SGMO) crystal lines are patterned on the surface of Sm2O3–Gd2O3–MoO3–B2O3 glasses by continuous wave Yb:YVO4 laser irradiations (wavelength is 1080 nm, power is 1.2 W and scanning speed is 5 μm/s). Crystal lines show self-organized periodic domain structures with periodic refractive index changes. The intensity of second harmonic (SH) waves changes periodically depending on the domain structure. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of SH intensities that the orientation of (MoO4)2− tetrahedra in SGMO crystals changes gradually and periodically along the crystal line growth direction due to the spontaneous strains in SGMO crystals.