Mechanism Of Domain Inversion Research Articles

Local domain inversion in MgO-doped lithium niobate by pyroelectric field-assisted femtosecond laser lithography

We explore a physical approach to invert ferroelectric domains in the volume of MgO-doped lithium niobate crystals without any external electric field. Permanent defect structures are created by focused infrared femtosecond laser pulses below the material surface along the polar axis followed by a thermal treatment. This procedure leads to an inversion of ferroelectric domains beneath and above the laser-induced filaments up to the surfaces of the crystal. All domain walls are straight and up to 800 μm long. We measure the domain width in dependence on the length of the filaments and the writing energy. The smallest achieved domain width and the domain spacing is 1 μm. We propose a model taking into account the temperature dependence of the pyroelectric field and thermally activated bulk charges to explain the mechanism of domain inversion. Our findings pave the way to all-optical printing of arbitrary ferroelectric domain structures for nonlinear photonic applications.

Role of the Input Profile Asymmetry and the Chirp on the Propagation in Highly Dispersive and Nonlinear Fibers

We report the role played by the pulse shape asymmetry and the initial chirp on the propagation in highly dispersive single mode fibers and on the drastic spectral broadening well known as the supercontinuum generation (SCG) in highly nonlinear waveguides. We deal with finite energy Airy pulse (FEAP) for the asymmetric pulse and with the sech-type pulse for a compared study. We find that chirping an Airy pulse allows us to obtain asymmetric spectral outputs and the time domain inversion mechanism in optical systems. For the SCG analysis, the weakly truncated chirped FEAPs are more suitable than the common symmetric profiles to generate coherent and ultrabroadband spectra.

Direct-writing of inverted domains in lithium niobate using a continuous wave ultra violet laser

The inversion of ferroelectric domains in lithium niobate by a scanning focused ultra-violet laser beam (lambda = 244 nm) is demonstrated. The resulting domain patterns are interrogated using piezoresponse force microscopy and by chemical etching in hydrofluoric acid. Direct ultra-violet laser poling was observed in un-doped congruent, iron doped congruent and titanium in-diffused congruent lithium niobate single crystals. A model is proposed to explain the mechanism of domain inversion.

Study on Mechanism of Domain Inversion in LiNbO3 and LiTaO3 and Its Application of Memory-nm Size Domain Inversion by EB Irradiation-

The ferroelectric large capacity memory that made direction of the spontaneous polarization of domain inversion correspond to binary values of a memory can be considered as one of the new devices adapting domain inversion technology. This paper describes the feature of LiNbO3 (LN) and LiTaO3 (LT) crystals investigated mainly for the purpose of memory application, the mechanism of domain inversion control, and its applicability in large capacity memory. LT crystal is considered to be a suitable material for nm-size polarization control memory, and this paper describes that the electron beam polarization controlling method is one of the methods effective for nm-size polarization control. Specifically, if thin LT crystal layer with a thickness of 1 μm can be formed, very small polarization structure with a diameter of less than 3 nm could be realizable. If polarization control of 1 dot is carried out into 10 nm × 10 nm region, a super-large capacity memory with a density of 1 T bit/cm2 may be realized.

Fabrication of Periodic Domain-Inversion in X-cut LiTaO3 by Heat Treatment Technique in an Electric Field

In this paper, we report a new fabrication technique, which makes it possible to obtain a deep and uniform periodic domain-inverted structure in X-cut LiTaO3. The structure is fabricated on an X-cut LiTaO3 crystal, in which a periodical proton-exchange region has been previously formed, by heat treatment under an added external electrostatic field. It is found that a uniform period of 10.8 µm can be obtained by this method. The generation mechanism of domain-inversion is also examined. It is observed that an electric field is essentially effective not only in the proton-exchange region where the temperature is above the Curie temperature (Tc) but also in the neighboring region where the coercive field is lowered by proton-diffusion. Our result also shows that the stronger the strength of an applied electric field, the deeper the depth of domain-inversion grows.

Role of stoichiometric point defect in electric-field-poling lithium niobate

Non-congruent LiNbO3 crystals has been used to determine the influence of the intrinsic defect density in the ferroelectric domain inversion mechanism. The poling processes have been carried out either at high temperature or at RT throughout the electric-field-poling technique. It is shown that the coercive field of LiNbO3 crystals is strongly influenced by the intrinsic defect density in the crystals. Moreover it is shown that it is possible to realign the ferroelectric domain structure of near-stoichiometric LiNbO3 crystals to prepare periodic poled structures which allows second harmonic generation at shorter wavelengths than with congruent crystals at a fixed wavelength.

Domain-inversion study of proton-exchanged linbo3 by means of transmission electron microscopy

Domain-inverted region in LiNbO3 single crystal were formed by proton exchange followed by heat treatment. Direct observation of the domain-inverted region is performed by using transmission electron microscopy (TEM). A charged straight 180-domain boundary was revealed and compared with winding domain boundaries in LiNbO3 grown by Czochralski method. Obtained results are significant to study the mechanism of domain inversion and morphology of inversion domains.

Study on domain inversion in LiNbO3 by Ti-indiffusion

In this paper, the fabrication of periodic domain inversion on the +C face of LiNbOs by Ti-indiflusion method has been presented. The influence of different gases and varying heat treatment times on domain inversion has been investigated. The mechanism of domain inversion has been discussed.

Direct Observation of Domain-Inverted Regions in Proton-Exchanged LiNbO3 Using Transmission Electron Microscopy

Direct observation of the domain-inverted regions in LiNbO3 formed by proton exchange followed by heat treatment is performed by using transmission electron microscopy. A charged straight 180° twinning domain boundary was revealed and compared with winding domain boundaries in LiNbO3 grown by Czochralski method. Obtained results are significant to studying the mechanism of domain inversion and morphology of inversion domains.

Domain inversion by Li2O out-diffusion or proton exchange followed by heat treatment in LiTaO3 and LiNbO3

Experimental studies on the domain inversion in LiTaO 3 by Li 2 O out-diffusion or proton exchange followed by heat treatment at high temperatures are performed. According to our experiments and the results previously obtained in LiNbO 3 , a relationship between the domain inversion and Li 2 O out-diffusion or proton exchange followed by heat treatment is assumed. An internal electric field model is proposed, which is based on the concentration gradient of lithium vacancies and protons. The domain inversion mechanism related to the two fabricating methods is explained for LiNbO 3 (LN) and LiTaO 3 (LT) by the tentative use of the model.

Study on the formation mechanism of a complex domain structure in LiNbO3

A complex domain structure in LiNbO3 is fabricated by proton exchange followed by heat treatment. Domain inversion at the +c and −c faces as well as reinversion in the inverted region near the +c surface are observed experimentally. The proton and lithium concentrations are measured by secondary ion mass spectroscopy. It is found that the proton profile peaks away from the surface due to indiffusion and outdiffusion. The domain inversion mechanism is discussed. An internal electric field model is proposed which is based on the concentration gradient of proton and lithium deficiency.

The mechanism for domain inversion in LiNbO3 by proton exchange and rapid heat treatment

Domain-inverted structures in LiNbO3 are fabricated by proton exchange followed by rapid heat treatment. The domain inversion mechanism is discussed in relationship to the pyroelectric field and to the concentration gradient of protons.

Multiple-crystal x-ray topographic characterization of periodically domain-inverted KTiOPO4 crystal

A periodically domain-inverted KTiOPO4 crystal has been characterized for the first time by multiple-crystal multiple-reflection x-ray topography. The striation contrast within the domain- inverted regions has been revealed in high strain-sensitivity reflection topographs. The origin of formation of the striation contrast and the mechanism of domain inversion in KTiOPO4 are discussed in terms of the structural characteristics of KTiOPO4.

Studies on Domain Inversion in LiNbO3and LiTaO3

AbstractDomain inverted structures in LiNbO3 (LN) and LiTaO3 (LT) are fabricated by proton exchange followed by rapid heat treatment. The formation and development of the effects of pyroelectric field on domain inversion are investigated. The proton and lithium profiles are measured by SIMS. The Curie temperature of the proton exchanged LT is evaluated by DSC. An internal electric field model is proposed to explain the domain inversion mechanism.

Low-Frequency Dielectric Responses of Proton-Exchanged LiTaO3

A space charge field model has been proposed for explaining the mechanism of domain inversion caused by heat treatment in proton-exchanged LiTaO3. The purpose of this study is to examine the existence of the space charges caused by proton exchange of LiTaO3. The low-frequency dielectric responses of proton-exchanged LiTaO3 measured at high temperatures are presented. It is shown that the dielectric constant and the dielectric loss are about one order of magnitude greater than those of unprocessed plates, and that the activation energy of proton-exchanged plates is different from that of unprocessed plates. These results indicate that a different species of defects arises in LiTaO3 due to proton exchange, and this results in a drastic increase of charged point defects.