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Large scale micro-structured optical second harmonic generation response imprinted on glass surface by thermal poling
Abstract
Micro-structured second harmonic generation responses have been achieved on borophosphate
niobium glasses by thermal poling using micro-patterned silicon substrates. The poling imprinting
process has created sub-micrometer sized patterns of both surface relief and second order optical
responses on the anode glass surface. Field enhancement effects within the micro structured
electrode are believed to govern the charge density on the glass surface during the process and thus
amplitudes of both implemented electric field and Maxwell stresses.
Supplementary resource (1)
... In contrast to the above methods, MTP is proposed as an efficient manufacturing method that can precisely customize the physical or chemical properties of micron-sized areas by controlling temperature fields, electric fields, and by using various imprinting modes without producing liquid or gaseous waste [22]. The MTP can be used for chemical reactivity modification [23], optical second harmonic generation [24][25][26], and GRIN microstructures preparation [17,[27][28][29][30]. The cations of the glass migrate during the MTP process, and subsequently, a space charge and a cationic depletion layer are formed after removing the poling voltage and heat [31,32]. ...
... When the U > 300 V, a breakdown of the thin air layer may occur. If so, uniform conducting plasma arisen in the air gap resulting in a weakening of the gap influence on the electric potential in the square area [25]. Once the U exceeds the breakdown voltage of the thin air layer, the electric potential in the square area approaches that in the grid line area. ...
Gradient refractive index (GRIN) micro-optics present unique opportunities for control of the chromatic properties, new degrees of freedom for optical design as well as the potential for use in new optical system applications. GRIN microgratings were imprinted in GeS2-Ga2S3-MCl (M = Na, K, Cs) chalcohalide glasses by microthermal poling, and the effects of the type and concentration of alkali cations on their performance were investigated. Two effective imprinting formation regions of the GRIN microstructure based on the poling saturation voltage (Us) and glass composition are observed at fixed poling time and temperature. The Us increases from 140 to 750 and 2600 V in accordance with the activation energy (Ea) of alkali ions (Na⁺ to K⁺ and Cs⁺) increasing from 45.15 to 58.62 and 92.58 kJ/mol for studied samples. The saturated numbers of diffraction order (Ns) of the gratings in these samples are 7, 9 and 6, respectively, the highest number being provided by the K⁺-containing sample. This is in accordance with imprinting-induced phase differences (0.14λ, 0.19λ and 0.09λ) measured in the fabricated samples containing Na⁺, K⁺ and Cs⁺ ions. Furthermore, the Us of samples decreases from 1500 to 300 V with four concentrations of K⁺ from 10 to 30%, associated with their Ea of K⁺ decreasing from 69.62 to 53.46 kJ/mol, while Ns increases from 8 to 14, which is attributed to the increase of the phase difference in the GRIN structures. The controllable GRIN microstructures are realized by adjusting the type and concentration of alkali cations in chalcohalide glasses, which is expected to drive the design of broadband GRIN microgratings.
... After years of research and experimentation on several families of cation-rich oxide glasses, like silicates [6,7], borates [8], boro-silicates [9][10][11], lead-borates [12][13][14], niobium boro-phosphates [15][16][17][18], alumino-phosphates [19], chalcogenides [20][21][22], tellurites [23][24][25], niobium germanates [26] and others, under different poling conditions and configurations, it became possible to achieve intense second harmonic (SH) signals, with χ (2) of the order of 5-8 pm/V, close to those produced by certain NL optical crystals like quartz or KDP. For instance, best results were obtained in sodium niobium boro-phosphate glasses [17] in which χ (2) was found equal to 5 pm/V. ...
... These calculated fractions are in good agreement with the NMR results on sodium diborate glass for which X B30 = 0.50, X B40 = 0.42 and X B31 = 0.08 [60]. The decrease of X B40 and the increase of X B31 in the simulation relative to experiment has been observed before for alkali borate glasses and was attributed to the Table 1 Values of the potential parameters used in the simulation; ionic radius, r i , number of valence electrons η i and charge z i of ion i. [14][15][16][17][18][19][20][21][22][23][24] higher fictive temperature in simulations [52,58,59]; as a consequence the equilibrium (7) shifts to the right as found also in the present case. ...
This work explores by molecular dynamics simulation the basic mechanisms and pathways that pertain to the induced optical nonlinearity in an ionic oxide glass due to electro-thermal poling. To the best of our knowledge, this is the first time where the kinetics combining the ion migration and the structural rearrangements is studied by using atomistic simulation. Most of the models published so far deal mainly with the charge transport effects, with no information provided on the kinetics of structural reorganization. To this aim, a simple borate glass doped with sodium cations was employed. Notwithstanding the small size of the specimen, due to computer time limitations, we were able to identify most of the experimental trends observed in different glass systems and under different poling conditions and configurations. They include the conversion of negatively charged structural units into neutral ones in the charge depletion region, a process reducing the excess negative charge after the migration of the mobile cations to the cathode, and the increased polymerization of the network close to the anodic surface. Taking into account the restrictions of our model, we also showed a mechanism for the generation of free oxygen species, due to the partial polarization of the Boron-Non-bridging oxygen (B-NBO) bonds along the embedded internal Direct Current (DC) electric field and their subsequent elongation and weakening.
... Surface topology is shown in Fig. 2(b). It can be clearly seen that the poled surface is reshaped with the formation of depleted strips placed below the anode edges: such relief creation does correspond to actual trenches of 200 nm depth induced by the electrostatic process [27][28][29][30]. Structural and chemical composition changes after poling process are widely discussed in Ref. [31], where it is stated that the migration of mobile cations such as sodium ions (Na + ) that move away from the anodes leads to the creation of a space charge. ...
Multiplex coherent anti-stokes Raman scattering (M-CARS) and second harmonic generation (SHG) techniques are used to map the real part of the nonresonant third order nonlinear optical susceptibility and the second order nonlinear optical susceptibility of a thermally microimprinted niobium borophosphate glass. In particular, such bimodal nonlinear imaging is employed in order to precisely evaluate how thermal poling can modify the amplitude of the nonresonant third-order nonlinearity of the sample. A systematic decrease of the M-CARS intensity is found in the poled areas with respect to the unpoled ones, suggesting therefore a reduction of the real part of the nonresonant third order nonlinear susceptibility within these regions. Such a reduction in the M-CARS intensity can be explained by sodium depletion in the subanodic zone and is mostly linked to the reduction of both the matter density and the linear refractive index, in agreement with earlier works on thermal poling on the same family of glasses.
... Complementing laser surface engineering methods to produce 2D (dimensional) or 2.5D structures, laser-induced bulk modification in transparent materials offers the possibility to add a large panel of new functionalities in the three dimensions of materials. This For monolayers irradiated with single laser pulses with conditions exceeding the material ablation threshold on each spot, the particles are ejected with the ablated products by a laser cleaning process and leave an array of nanoholes directly behind on the surface that is directly attractive for optical sensing or structuring applications [118][119][120][121]. This process is illustrated with Figure 6b, where the top SEM image shows an array of 500 nm diameter spheres partially irradiated with a nanosecond laser at a 193 nm wavelength. ...
... Complementing laser surface engineering methods to produce 2D (dimensional) or 2.5D structures, laser-induced bulk modification in transparent materials offers the possibility to add a large panel of new functionalities in the three dimensions of materials. This For monolayers irradiated with single laser pulses with conditions exceeding the material ablation threshold on each spot, the particles are ejected with the ablated products by a laser cleaning process and leave an array of nanoholes directly behind on the surface that is directly attractive for optical sensing or structuring applications [118][119][120][121]. This process is illustrated with Figure 6b, where the top SEM image shows an array of 500 nm diameter spheres partially irradiated with a nanosecond laser at a 193 nm wavelength. ...
Citation: Al-Kattan, A.; Grojo, D.; Drouet, C.; Mouskeftaras, A.; Delaporte, P.; Casanova, A.; Robin, J.D.; Magdinier, F.; Alloncle, P.; Constantinescu, C.; et al. Short-Pulse Lasers: A Versatile Tool in Creating Novel Nano-/Micro-Structures and Compositional Analysis for Healthcare and Wellbeing Challenges. Nanomaterials 2021, 11, 712. https://
... The region that was placed beneath the anode presents lower refractive index [3][4][5]. For these properties poled glass is used for waveguides [6], imprinting diffractive gratings on its surface [7][8][9][10], and also for etching because material from the poled region is more easily removed [11][12][13]. Recently, poled glass has been proposed as a substrate for microstructuring thin metal layers [14]. ...
Application of electric field and moderately elevated temperature depletes the side facing anode from alkali present in glasses. The change of composition of the treated glass results in variation of refractive index depth profile within the treated glass. Spectroscopic ellipsometry is employed for characterization of optical properties of glass treated in different conditions. The results of optical characterization are verified by secondary ion mass spectroscopy. It is found that the refractive index profile obtained from ellipsometry has a maximum value higher than the one of untreated glass. The obtained refractive index profiles are in very good agreement with concentration profiles.
Sodium tantalum germanate glasses were thermally poled using microstructured metallic anodes of two distinct geometries. Topological, structural and optical characterizations of the micro-imprinted structures revealed an accurate reproducibility of the...
The existence of optical nonlinear properties in silver‐oxide‐doped and ‐undoped germanotellurite glasses by using thermal poling treatment was demonstrated and compared. The variation of second‐order nonlinear optical characteristics with poling voltage and their stability with time were observed via the macroscopic second harmonic generation measurement. The study also includes the investigation of enhancement of the nonlinear property by thermally poling K[Nb1/3Te2/3]2O4.8 volume‐distributed glass‐ceramic composite in which the role of silver in ceramic component and the modified surface structure layer of the glass component would be further discussed.
Chalcohalide glasses with a gradient refractive index (GRIN) microstructure were imprinted by microthermal poling for realizing diffractive optical elements covering the visible to middle-infrared wavelength range. The effect of halogen ions on the saturation poling voltage (U), surface profile, diffraction pattern, optical transmittance, GRIN microstructure, and structural rearrangement of poled glass is investigated. An effective imprinting formation region for a GRIN microstructure based on the U and glass composition is observed under fixed poling time and temperature. The onset U (60 V to 150 V) and activation energy of mobile cations (0.449 eV to 0.533 eV) decreases with the atomic number of the halogen from F to I, but the saturation diffractive order (8th to 11th levels) and phase difference (~ 0.08λ to 0.18λ) increases accordingly. The onset U and activation energy decrease with the deformability of the glass network and radius of the halogen ions. The phase difference and saturation J o u r n a l P r e-p r o o f diffractive orders decrease with the proportion and electronegativity of interval halogen atoms in the glass network. Thus, chalcohalide glasses with GRIN microstructures can be tailored by adjusting the type of halogen ions for realizing various diffraction optical elements.
La description quantitative des phénomènes d’optique non linéaire nécessite de connaître la réponse du milieu de propagation à une excitation par un champ optique très intense. La connaissance de cette réponse se fait à travers la détermination des susceptibilités non linéaires du matériau. Dans ce cadre, cette thèse présente une méthode de mesure des susceptibilités non linéaires du second et du troisième ordre de matériaux oxydes inorganiques et d’échantillons biologiques. Cette méthode se base sur l’utilisation de la diffusion Raman anti-Stokes cohérente multiplexée en longueurs d’onde (M-CARS) et l’exploitation du bruit de fond non résonant qu’elle présente systématiquement afin de déterminer la composante électronique de la susceptibilité non linéaire d’ordre trois du matériau étudié. Cette approche est ensuite appliquée à l’imagerie multimodale non linéaire.
A microstructured SHG pattern on Sm 2 O 3-doped sodium borophosphate niobium (SmBPN) glasses was obtained by laser-induced thermal poling. The optical properties of SmBPN glasses were recorded by UV/Vis/NIR transmission spectra. In situ laser-induced heating of the SmBPN glasses without and with preheating was characterized by an infrared thermal camera. A laser-induced microstructured pattern was written on the ITO electrode, resulting in a local electric field enhancement during the poling process. Laser-induced heating together with the enhanced local electric field of the microstructured electrode governed the geometry and strength of the electrical field of these SmBPN glasses. This poling process could be a potential method to design second-order optical properties or even to fabricate microstructures.
A diffractive optical element (DOE) covering visible to middle-infrared regions is imprinted in chalcohalide glass by microthermal poling under ultralow voltages (~125 V). The effect of the poling voltage on the surface profiling, optical diffraction, optical transmittance, and anode-side structural rearrangement is investigated. Deformation of the surface profiling and diffraction order increase with increasing poling voltage, showing a saturation voltage of 125 V and a decrease in the transmittance within 10%. In addition to the normal vertical migration of silver ions, an obvious and unexpected transverse migration of silver ions and mutual structural transformation occur between homopolar bonds Ge–Ge (Ga–Ga) and S–S and the heteropolar bond Ge–S (Ga–S), which are key to forming the surface profiling and subsurface structures. Formation of the DOE mainly depends on the periodic subsurface microstructure rather than surface profiling. Thus, simple and inexpensive processes can fabricate broadband wavelength-based DOEs for military, medical and biological applications.
Second-order optical susceptibility, χ⁽²⁾, has been induced in thermally poled chalcogenide glasses, doped with varying levels of sodium. Using alkali-doped chalcogenide glasses, the second harmonic generation (SHG) capability is retained for over a year whereas in alkali-free glasses it disappears in days. The enhanced stability is attributed to a stabilization of the space charge through structural re-arrangements. Polarization-resolved SHG shows that the induced electric field has components in three spatial directions, all with varying extents of stability. Using structured electrodes, we demonstrate the ability to control the various electric field components’ geometry, location and stability to realize a long-lived, nonlinear grating in an alkali-doped chalcogenide glass.
Current status of studies devoted to thermal poling of multicomponent glasses and related applications are briefly reviewed. Physical phenomena occurring in the course of the poling manifest themselves in second harmonic generation (SHG), linear electrooptical effect, formation of surface and refractive index relief and changes of chemical properties of poled glasses. All these effects can be used for structuring of the glass surface and glass-metal nanocomposites in the terms of chemical reactivity, SHG, formation of diffraction gratings, and growth of ordered metal nanoparticles. Both literary data and results of own researches of the authors are presented.
Relief diffraction gratings are formed via acidic chemical etching of a periodically poled soda-lime glass. The thermal poling under 1000 V DC is performed at 325 °C using a thermally stable glassy-carbon anodic electrode with periodic grooves, the depth of the grooves being of ∼650 nm. Poling-induced modification of the glass results in deepening the glass anodic surface in the regions under the ribs of the anodic electrode due to volume relaxation and in increasing chemical durability of these regions in acidic media comparatively to the virgin glass. Chemical etching of the poled glass in NH4F:8H2O solution allows additional to the thermal poling shaping of the glass surface via faster dissolution of unpoled/less poled glass regions. The morphology of the glass surface before and after the etching is characterized with atomic force and scanning electron microscopy. About 30 min etching provides the formation of ∼0.9 μm in height relief diffraction gratings with the diffraction efficiency close to the theoretically achievable ∼30% for multi-order diffraction. In vivo measuring of the diffraction efficiency in the course of the etching allows precise fabrication of the gratings.
Thermal poling was proven successful to induce second order nonlinear properties and concurrent modification of composition, structure and chemical reactivity in glasses. With current efforts to reduce devices sizes in components employing such attributes, means to control changes at the micrometer scale are needed. We present a micro-imprinting poling process to locally tailor surface properties of a glass. Measurements using infrared, Raman and second harmonic generation microscopies confirm that changes in glass structure associated with an induced static electric field are responsible for the enhanced surface reactivity that is successfully controlled at the micrometer scale.
Imprinting the relief of anodic electrode in glass surface in the course of DC electric field polarization of the glass is studied using atomic force microscopy. Square grid with rectangular relief produced on silicon by e-beam lithography and ion etching (relief height 120 nm, line width 0.5 μm, and periodicity 1 μm), and lead-silicate glass microchannel plate (channel diameter 9.5 μm and distance between the channels 12.5 μn) possessing electronic conductivity along the channels walls were used as anodic electrodes. The height of the relief formed on glass surface after polarization varied from 5 to 15 nm depending on the conditions of the processing. The mechanism of relief formation is discussed.
The thermal poling technique was applied to optical waveguides embedded in a commercial boro-aluminosilicate glass, resulting in high levels of induced second-order optical nonlinearity. The waveguides were fabricated using the femtosecond laser direct-write technique, and thermally poled samples were characterized with second harmonic optical microscopy to reveal the distribution profile of the induced nonlinearity. It was found that, in contrast to fused silica, the presence of waveguides in boro-aluminosilicate glass led to an enhancement of the creation of the second-order nonlinearity, which is larger in the laser written waveguiding regions when compared to the un-modified substrate. The magnitude of the nonlinear coefficient d 33 achieved in the core of the laser-written waveguides, up to 0.2 pm/V, was comparable to that in thermally poled fused silica, enabling the realization of compact integrated electro-optic devices in boro-aluminosilicate glasses.
Large arrays of sub-micrometre blind holes and with a filling ratio up to 60% on areas of millimetre square are realized on silicon. The structuration ensues from combining both Langmuir–Blodgett deposition technique and ultraviolet nanosecond laser-assisted photonic nanojet ablation through C18 functionalized silica microspheres. Different laser fluence ranges and numbers of laser shots are studied to understand the tradeoff between size, quality of the craters and surface morphology after laser irradiation. In particular, tuning the irradiation fluence yields selectivity of the characteristic lateral dimension of the imprinted craters on the substrate and laser operation in multishot mode allows obtaining high quality and regularity of the surface morphology of the resulting millimetre square arrays of holes. This simple, fast, long-range and low-cost near-field nanolithography technique is of interest for fabricating devices with new functionalities and finds applications in many fields in nanoscience and nanoengineering.
The formation of a spatial relief reproducing that of the anode as a result of the thermal poling of glasses and glass-metal
nanocomposites in a strong electric field has been studied by atomic force microscopy. The anode surface patterns exhibited
either a square grid or a rectangular grating with a depth of 120 nm, a strip width of 0.5 μm, and a period of 1 μm manufactured
using electron-beam lithography and ion etching on the surface of an n-type single crystal silicon wafer. The relief depth formed on the surface of poled samples varied within 5–15 nm, depending
on the experimental conditions. The mechanism of relief formation in this system is discussed.
The objective to induce reproducible, efficient, and stable second-order nonlinear optical properties (SONL) in an isotropic material remains a challenge in photonics. Thermal poling allows inducing SONL properties in glasses by the formation of an axial symmetry because of the implementation of a static electric field within the glassy matrix. A description of the main poling mechanisms is proposed. Depending on the glass compositions and the poling conditions, an effort is made to correlate poling mechanisms and the strength of the implemented static electric field. A review of the main technological improvements done to develop poled-silica-based electro-optical modulators as well as the SONL efficiencies obtained for different glass compositions is reported and analyzed.
Thermal poling of silica glass modified by femtosecond laser irradiation is demonstrated. Increase of second-harmonic generation in the irradiated regions is observed. This enhancement is interpreted in terms of structural modifications in silica glass that make the poling process more efficient. Evidence of a change in the distribution of the electrostatic field frozen in glass during poling is obtained. This technique is used for chi((2)) grating fabrication. (C) 2002 American Institute of Physics.
Micro-Raman analysis has been carried out on the cross section of thermally poled sodium-niobium borophosphate glasses. We were able to measure with accuracy an enhanced Raman response from the nonlinear optical (NLO) layer formed at the anode side of the poled glasses. The thickness of the NLO layer has been estimated. Several spectral changes were observed within this layer, which manifest important structural rearrangements after thermal poling. Possible mechanisms leading to structural reorganization in the space charge region are discussed.
We report that it is possible to create a fiber electret by having both internal electrodes of a twin-hole fiber at the same anodic potential, i.e., without the use of a contacted cathode electrode. We find that a stronger and more temperature-stable charge distribution results when the fiber core is subjected to an external field near zero. Negative charges from the air surrounding the fiber are sufficient for the recording of an electric field across the core of the fiber that is twice stronger than when one anode and one cathode electrode are used. The enhancement in stability and in the strength of the effective chi((2)) induced are a significant step towards the wider use of fibers with a second order optical nonlinearity.
In this paper, we investigate the contribution of deep and shallow trapped ions on the second-order nonlinearity during typical poling procedures in soda-lime glass. The zero-electric field potential barriers of each contribution were estimated. The shallow traps, measured through the electrical ionic current, was determined as ~0.34 eV; while deep trap activation energy, measured by means of the thermal/electric field activated luminescence, was estimated ~3.8 eV. The traps show different dependence on its thermal energy onset for different applied electric field. The ionic current is linearly dependent on the electric field. The luminescence has a minimum electric field ~3.6 kV/cm and thermal energy ~31 meV (~87 degrees C) to occur. The average ionic jump lengths for both processes are also estimated, and the deep trap length is about ten times shorter than the shallow trap one. Samples poled at the border of the luminescence onset parameters revealed that the higher its contributions the more stable the induced second order nonlinearity.
Channel waveguides were formed on fused silica substrate by Ge-ion implantation with lithographically defined channels. Thermal poling was performed to form second order optical nonlinearity (SON) in the waveguides. Periodical photo masks were designed and fabricated on a mask glass. Periodical erasure of the SON in the channel waveguides by 266 nm UV light with the photo mask on the fused silica substrate produced periodical SON distribution in the waveguides. First order quasi-phase-matching second-harmonic generation from 1064 nm to 532 nm was demonstrated in the channel waveguides.
Quasi-phase matched second-harmonic generation at 532 nm is demonstrated in a channel waveguide that is written in bulk fused silica using a femtosecond laser. The second-order nonlinear grating is fabricated using uniform thermal poling followed by periodic erasure inside an e-beam deposition system caused, by what we believe to be, x-rays. A SHG conversion efficiency of 2 x 10(-5) %/W-cm(2) was obtained for a 1 cm long device, corresponding to an effective nonlinear coefficient of 0.0075 pm/V. (C) 2009 Optical Society of America
Second-harmonic generation in 60GeS(2)-2OGa(2)S(3)-20KBr chalcohalide glass was investigated by the thermal poling method. A large second-order nonlinear susceptibility, as high as 7.0 pm/V, was obtained in a poled sample by Maker fringe analysis. We believe this to be the first time that a clear second-harmonic wave was observed in chalcohalide glasses containing large amount of alkali ions (6.25 at. %). Such observation is of great potential use in all optical waveguide devices. (c) 2006 Optical Society of America.
Active mode-locking of a fiber laser with an all-fiber electrooptic modulator is demonstrated. A 1.4-V driving signal was used, creating subnanosecond single pulses at the fundamental frequency of the cavity (12 MHz). The modulator was a packaged Mach-Zehnder interferometer incorporating a poled twin-hole fiber in one of the arms. The switching voltage was 230 V at 1550 nm, with extinction ratio ∼20 dB. The interferometer could be electrooptically tuned by 3.5 nm.
An experimental study on nitrogen oxides (NOx) removal from a simulated diesel engine exhaust gas was carried out in geometry of various electrodes for dielectric barrier discharge reactor to improve the removal efficiency. The electrodes employed in the experiment were a plane, a trench, and a multipoint geometry. The right-pyramids, which were used as multipoint, had 45° tip angle and a height of 1-5 mm. The multipoint electrodes have 528-5000 pyramids in an area of 132 cm<sup>2</sup> (22 × 6 cm). The trench electrode has knife-edge rails with 5-mm height and 45° tip angle. The alumina dielectric barrier coated plane electrode was used as a high-voltage electrode, to which a sinusoidal high voltage was applied with frequency of several tens kilohertz. The N<sub>2</sub>:O<sub>2</sub>=9:1 mixed gas containing 200-ppm NO was used as simulated gas with gas flow rate of 5 L/min. NO removals in case of the plane and the trench electrodes were lower than that in case of multipoint one. NO removal yield drastically decreases with increasing the number of pyramids on the electrode. NO removal efficiency was almost independent of the pyramid projection height under our experimental condition.
Molecular and ionic species of nitrogen oxides have been injected, formed, and then trapped within a borosilicate glass during a thermal poling process. This original observation denotes a new aspect of poling mechanisms for ionic glasses. For each poled borosilicate glasses studied, compositional, structural, and second harmonic generation profiles of their subanodic polarized layers have been characterized. A description of the space charge implementation process, involving interactions between charged and chemically active species formed both within plasma discharges at the glass/electrode interface and within the polarized glass matrix, is proposed.
The process of poling of silica glass using periodical anodic electrode, or, the same, electric field imprinting of periodical structure in silica glass is modeled. We studied the influence of the electrode periodicity and the magnitude of applied voltage on the thickness of poled (charge carriers depleted) region and on the smearing of the relief of the poled region. It is shown that the smearing is mainly limited by charge carriers drift induced by lateral components of electric field formed by the anodic electrode. The modeling also shows that if high, order of kilovolts, voltage is used for poling, the atmosphere and the type of anodic electrode (blocking or non-blocking) do not essentially influence the results of the processing.
Information about the origin of the optical non-linear response in transparent glasses can be gained from a detailed structure investigation using Raman and X-ray absorption spectroscopies. The effects resulting from the introduction of niobium oxide in the sodium borophosphate matrix of composition 0.95NaPO30.05Na2B4O7 are described. For small niobium concentrations, the formation of distorted NbO6 octahedra is observed. The increase of niobium concentration allows the progressive linking of corner-shared and less distorted octahedra. The correlative evolution of the measured third order susceptibilities χ(3) is analyzed on the basis of the bond orbital theory. A good agreement between experimental and calculated χ(3) is obtained as long as the NbO6 entities are isolated from each other, but the clustering of these entities increases the non-linear response, χ(3).
A general new 4(n+1)×4(n+1) matrix formulation of Maker fringes applicable to any anisotropic material containing n layers, convenient and straightforward for experimental data analyses, is proposed. The treatment of the transmitted and reflected harmonic waves includes the contribution of anisotropic one-photon absorption for the fundamental and harmonic waves under the assumption of no pump depletion and leads to a complete analysis of any linearly or elliptically polarized harmonic signal recorded under various incident polarization configurations. In the framework of the proposed model, we report detailed results of Maker fringes in various samples, for instance, in one and two z-cut quartz plates separated by a controlled air gap.
In usual thermal imprint process, mold patterns are transferred by applying mechanical pressures at elevated temperatures. We have developed a new imprint process for glass, which utilizes electrostatic force as a driving force for deformation. In the method, high dc voltage is applied between a mold and a glass specimen so that the mold becomes an anode. This method enables glass forming at lower temperatures with smaller mechanical force compared to usual thermal imprint process. In addition, this method is suitable for small patterns less than 1 mum. It is expected that this method realizes large-area and high-efficiency nano-forming process for glass.
In general corona discharge is used as precharger in electrostatic precipitator (ESP). The corona discharge type electrostatic precipitator can remove diesel exhaust particles (DEP) at high efficiency but at low efficiency for NOx. We propose here a barrier discharge type ESP which gives a high removal efficiency for both NOx and DEP. To study the influence of electrode shape of precharger on the collection efficiency, we carried out experiments using metallic electrodes with/without punched holes as a barrier discharge electrode. As results, discharge current was higher for the electrode with punched holes than for plane electrode. The collection efficiency obtained with punched electrode was higher than that with at plane electrode. In the next step, additionally change of metallic electrode shape, and then discharge current and performance are evaluated.
Devices in periodically poled glass must have a large periodic variation of the built-in field. We show that the periodic variation can be severely degraded by charge dynamics taking place at the external (glass-air) interface or at internal (glass-glass) interfaces if the interfaces have imperfections. The problem of the external interface can be solved by poling with periodic electrodes that are buried inside the glass, in many cases improving the poling efficiency dramatically. Internal interfaces can be addressed by the proper choice of waveguide design and processing. Without poling the device, one can reveal the existence of imperfect interfaces by use of electric field induced second-harmonic generation.
Thermal poling of sodium borophosphate niobium glasses, previously coated with a thin silver layer micropatterned by femtosecond laser irradiation, is demonstrated. The field-assisted ion-exchange process for fabricating planar surface in this glass substrate is analyzed. Inside the silver ablated lines obtained by femtosecond laser irradiation, we clearly observe a change in the distribution of the frozen electrostatic field that is modulated by the Ag+/Na+ ion-exchange process during the thermal poling.
High second-order susceptibilities are created by thermal poling in bulk germanium disulfide based chalcogenide glasses. Experimental conditions of the poling treatment (temperature, voltage, time) were optimized for each glass composition. The second-order nonlinear signals were recorded by using the Maker fringes experiment and a second-order coefficient χ(2) up to 8 pm V–1 was measured in the Ge25Sb10S65 glass. This value is obtained using a simulation based on accurate knowledge of the thickness of the nonlinear layer. Two mechanisms are proposed to explain the creation of a nonlinear layer under the anode: the formation and the migration of charged defects towards the anode may mainly occur in Ge20Ga5Sb10S65 and Ge25Ga5S70 glasses, whereas the migration of Na+ ions towards the cathode may be responsible for the accumulation of negative charges under the anode in Ge33S67 and Ge25Sb10S65 glasses. Different electronic conductivity behaviors seem to be at the origin of the phenomenon. In parallel, the potential effect of the poling treatment on the structural and electronic properties is studied using Raman spectroscopy and secondary ion mass spectroscopy measurements.
Thermal-electric field poling of soda-lime glasses with modulated applied voltage based on the peculiar dependence of the electroluminescence activation energy is investigated. The second order nonlinearity (SON) stability upon infrared laser pump has show an abrupt change for poling voltage of ∼900 V . The contributions to the onset of the SON are treated concerning the general random-energy model for ionic transport in ionic glasses. Corona effect and electroluminescence in thermal-electric field poling in soda-lime glasses are also investigated. The corona and electroluminescence spectra exhibit noticeable difference only in the 185–300 nm region where the former is absent.
Transparent and homogeneous sodium borophosphate niobium glasses with good optical quality were obtained for Nb2O5 proportion up to 50 mol%. Large NLO second-order susceptibilities, up to ∼5 pm/V for the highest niobium loading, are generated through an efficient thermal poling process which induces a strong space-charge migration of Na+ cations. From combined IR, Raman and thermal analyses, we establish that the observed strong increase of χ(2) responses with niobium concentration is linked to the extent of the niobium–oxygen 3D structure which enhances the third-order susceptibility.
Measurements of the transient behavior of both the second-harmonic generation signal and the poling current for type-II fused silica samples under a variety of poling histories are reported. The applied voltage was switched between +5 kV, 0 V, and −5 kV with the sample maintained at 275°C. Observations include: multiple time scales (seconds to minutes) for development of the non-linearity depending on the poling history; a transient second-harmonic signal on the new cathode side of the sample following voltage reversal; and hysteretic incubation intervals before growth of the non-linearity. These observations are incompatible with the usual single mobile ion (e.g. Na+) model for establishing the strong local electric field that leads to the non-linearity. An expanded model including ion-exchange between a high mobility ion (as Na+) and a much lower mobility ion (related to H+) provides a good qualitative fit to the experiments.
A large second-order nonlinearity [chi((2)) 1 pm/V 0.2 chi((2)) (22) for LiNbO(3)] is induced in the near-surface ( 4 microm) region of commercial fused-silica optical flats by a temperature (250-325 degrees C) and electric-field (E ~ 5 x 10(4) V/cm) poling process. Once formed, the nonlinearity, which is roughly 10(3)-10(4) times larger than that found in fiber second-harmonic experiments, is extremely stable at room temperature and laboratory ambient. The nonlinearity can be cycled by repeated depoling (temperature only) and repoling (temperature and electric field) processes without history effects. Possible mechanisms, including nonlinear moieties and electric-field-induced second-order nonlinearities, are discussed.
We demonstrate that frequency-converting devices of high quality can be realised with glass poling. The devices, made with silica-onsilicon technology, are poled with periodic, embedded electrodes, and used for second-harmonic generation. We obtain precise control of the quasi phase-matching wavelength and bandwidth, and a normalised conversion efficiency of 1.4 x 10(-3) %/W/cm(2) which, to our knowledge, is the highest obtained so far with periodic glass poling. (c) 2005 Optical Society of America.
Second harmonic generation (SHG) has been obtained in a rich in sodium niobium orophosphate glass by a thermal poling treatment. The thermally poled glass SHG signal has been studied through an original analysis of both transmitted and reflected polarized Maker-fringe patterns. Therefore, the second order nonlinear optical (NLO) efficiency was estimated from the simulation of the Maker-fringe patterns with a stepwise decreasing profile from the anode surface. A reproducible chi(2) susceptibility value as high as 5.0 +/-0.3 pm/V was achieved at the anode side. The nonlinear layer, found to be sodium-depleted up to 5 microm deep inside the anode side, identical to the simulated nonlinear zone thickness, indicates a complex space-charge-migration/ nonlinear glass matrix response process.
Molten alloys under high pressure were used to obtain fibers with long internal electrodes that are solid at room temperature. An integrated Mach-Zehnder interferometer was constructed from a twin-core twin-hole fiber that permitted application of an electric field preferentially to one of the cores. Good stability and a switching voltage of 1.4kV were measured with a 1-m-long fiber device with a quadratic voltage dependence.
Second-harmonic generation, one of the second-order nonlinear optical properties of thermally and electrically poled WO>(3)-TeO>(2) glasses, has been examined. We poled glass samples with two thicknesses (0.60 and 0.86 mm) at various temperatures to explore the effects of external electric field strength and poling temperature on second-order nonlinearity. The dependence of second-harmonic intensity on the poling temperature is maximum at a specific poling temperature. A second-order nonlinear susceptibility of 2.1 pm/V was attained for the 0.60-mm-thick glass poled at 250 degrees C. This value is fairly large compared with those for poled silica and tellurite glasses reported thus far. We speculate that the large third-order nonlinear susceptibility of WO>(3)- TeO>(2) glasses gives rise to the large second-order nonlinearity by means of a X((2)) = 3X((3)) E(dc) process.
We fabricated second-order nonlinear gratings in D-shaped germanosilicate fibers, using thermal poling and periodic electrodes defined by standard photolithography. These gratings, which are up to 75 mm long, were used for efficient quasi-phase-matched frequency doubling of 1.532-mum nanosecond pulses from a high-power erbium-doped fiber amplifier. Average second-harmonic powers as high as 6.8 mW and peak powers greater than 1.2 kW at 766 nm were generated, with average and peak conversion efficiencies as high as 21% and 30%, respectively.
A theoretical formalism designed to quantify linear optical and second-order nonlinear optical responses of achiral or chiral anisotropic materials in planar structure is presented. In particular, the theory includes linear optical activity that is governed by the gyrotropic components and second-harmonic generation optical rotatory dispersion, the magnitude of which depends on the ratio of chiral and achiral chi((2)) components. Examples are given which reproduce complex interference effects and other subtle optical effects that are encountered in layered structures. Detailed experimental second harmonic generation studies of quartz and dihydrogen phosphate that quantify linear and nonlinear optical activities of these materials are reported.
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J. Appl. Phys. 118, 043105 (2015)
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Chalcogenide glasses based on germanium disulfide for second harmonic generation
- V Guignard
- F Nazabal
- J L Smektala
- O Adam
- C Bohnke
- A Duverger
- H Mor Eac
- A Zeghlache
- G Kudlinski
- Y Martinelli
- Quiquempois
Guignard, V. Nazabal, F. Smektala, J. L. Adam, O. Bohnke, C.
Duverger, A. Mor eac, H. Zeghlache, A. Kudlinski, G. Martinelli, and Y.
Quiquempois, "Chalcogenide glasses based on germanium disulfide for
second harmonic generation," Adv. Funct. Mater. 17, 3284-3294
(2007).