Pockels Effect Research Articles

Simultaneous measurements of temporal evolutions of the voltage and the current on the load of the Seoul National University X-pinch device using the optics-based systems.

Optics-based measurement systems have been developed to measure the voltage and the current on a load of the Seoul National University X-pinch device [Ryu etal., Rev. Sci. Instrum. 92, 053533 (2021)]. A lithium niobate crystal that changes the polarization state of the propagating laser beam due to the Pockels effect induced by the electric field across the crystal, thus capable of measuring the voltage, is located next to the load. For the current measurement, an optic fiber is wound around the load to detect the change in the polarization state of the propagating laser beam due to the Faraday rotation induced by the magnetic field. As both voltage and current measurement systems utilize optical effects, the sensors, i.e., the lithium niobate crystal and the optic fiber, do not require any electrical grounds, in contrast to circuit-based probes, such as voltage dividers or Rogowski grooves. This facilitates an easy access to shield other required electronic devices, such as lasers and photodetectors, from the electromagnetic interference generated by the X-pinch power system. In addition, the sensors can be placed in close proximity to the load with fewer concerns on the electrical insulation. Temporal evolutions of the simultaneously measured voltage and current on the load of the X-pinch are successfully obtained and discussed.

Styrene monomer as potential material for design of new optoelectronic and nonlinear optical polymers: density functional theory study.

Using density functional theory, we have studied the intrinsic properties of styrene. First, we determine the optimized structures, structural parameters and thermodynamic properties to make our simulations more realistic to experimental results and check the stability. Second, we investigate optoelectronic, electronic and global descriptors, transport properties of holes and electrons, natural bond orbital analysis, absorption and fluorescence properties. Finally, we study nonlinear optical (NLO) properties: first- and second-order hyperpolarizability, second and third-order optical susceptibilities, hyper-Rayleigh scattering hyperpolarizability, electro-optical Pockel effect, direct current Kerr effects and quadratic refractive index. The bandgap energy E g = 5.146 eV and dielectric constant show that styrene is a good insulator with an average electric field value of 4.43 × 108 Vm-1. Thermodynamic findings show that our molecule is thermodynamically and chemically stable. Electron and hole reorganization energies of 0.393 and 0.295 eV, respectively, show that styrene is more favourable to hole transport than electron transport. Styrene is transparent with linear refractive index n = 1.750 and quadratic n 2 = 1.748 × 10-20 m2 W-1. At the NLO, styrene has a non-zero value of which confirms the existence of first-order NLO activity. Globally the study shows that the styrene monomer is suitable for the architecture design of new polymer materials for NLO applications and optoelectronic by functionalization.

Mid-infrared barium titanate electro-optic modulators based on a germanium-on-silicon platform

Mid-infrared electro-optic (EO) modulation efficiency and high-frequency performance of barium titanate (BTO) modulators on a germanium-on-silicon platform are investigated. Leveraging its exceptional Pockels coefficients, BTO exhibits remarkable EO modulation capabilities in both transverse-electric (TE) mode for a-axis growth and transverse-magnetic (TM) mode for c-axis growth. At the wavelength of 3.8 µm, the V π ⋅L for a-axis oriented BTO (TE polarization) is 1.90 V·cm, and for c-axis oriented BTO (TM polarization), it is 2.32 V·cm, which have better performance than those of the Pockels effect based EO modulators from literature. In addition, the high-frequency EO response of the modulator is simulated, and a 3-dB EO bandwidth of 62.82 GHz with the optimized traveling wave electrodes is achieved, showing promise in the high-speed MIR applications such as free-space optical communications.

Effect of nitrogen/oxygen ratios on surface charge distributions generated by repetitive surface dielectric barrier discharges

Studies on the dielectric surface parameters and dielectric barrier discharges (DBD) characteristics considering the influence of gases in DBD on the surface charge distribution are scarce. Thus, to overcome this research gap, this study measured the potential distributions of AC-driven surface DBD in oxygen (O2), synthetic air and nitrogen (N2) as background gases using the Pockels effect. The results showed that the patterns of the filamentary discharges generated during the positive voltage polarity phase differed depending on the O2 ratio. In addition, the electrostatic repulsion forces between the residual charge and the newly created filament were analysed from the measured potential distribution and the greatest effect was observed in air, rather than in N2 and O2. The potential distribution was transformed into a charge density distribution and compared with the discharge luminescence in air and N2. The results showed that the shape of the filament tip differed between the charge density and discharge luminescence only in the case of air, which was attributed to the effect of attachment reactions on the formation of residual charge. The measurements showed that in a surface discharge, similar to the case in a volume discharge, the photoionisation and ionisation coefficients significantly affected the geometrical properties of the discharges.

A Novel Proposal of an Electro-Optical Sensor to Measure Various Levels of an Electric Field Using Pockels Effect Photonic Crystals

Electro-optic sensors based on the Pockels effect are key components for optical instrumentation due to their speed and accuracy. In this work, we propose a new electro-optic platform using two-dimensional photonic crystals of gallium arsenide and barium titanate (GaAs-BTO). This structure allows for the measurement of various electric field levels, from 0 kV/mm to 50 kV/mm, with a very high sensitivity and a compact size. The opto-geometric parameters of this sensor were chosen, optimized, and analyzed numerically using the Plane Wave Expansion (PWE) and Finite-Difference Time-Domain (FDTD) methods.

Physics to system-level modeling of silicon-organic-hybrid nanophotonic devices

The continuous growth in data volume has sparked interest in silicon-organic-hybrid (SOH) nanophotonic devices integrated into silicon photonic integrated circuits (PICs). SOH devices offer improved speed and energy efficiency compared to silicon photonics devices. However, a comprehensive and accurate modeling methodology of SOH devices, such as modulators corroborating experimental results, is lacking. While some preliminary modeling approaches for SOH devices exist, their reliance on theoretical and numerical methodologies, along with a lack of compatibility with electronic design automation (EDA), hinders their seamless and rapid integration with silicon PICs. Here, we develop a phenomenological, building-block-based SOH PICs simulation methodology that spans from the physics to the system level, offering high accuracy, comprehensiveness, and EDA-style compatibility. Our model is also readily integrable and scalable, lending itself to the design of large-scale silicon PICs. Our proposed modeling methodology is agnostic and compatible with any photonics-electronics co-simulation software. We validate this methodology by comparing the characteristics of experimentally demonstrated SOH microring modulators (MRMs) and Mach Zehnder modulators with those obtained through simulation, demonstrating its ability to model various modulator topologies. We also show our methodology's ease and speed in modeling large-scale systems. As an illustrative example, we use our methodology to design and study a 3-channel SOH MRM-based wavelength-division (de)multiplexer, a widely used component in various applications, including neuromorphic computing, data center interconnects, communications, sensing, and switching networks. Our modeling approach is also compatible with other materials exhibiting the Pockels and Kerr effects. To our knowledge, this represents the first comprehensive physics-to-system-level EDA-compatible simulation methodology for SOH modulators.

DFT investigation of M2F superalkali doped dodecafluorophenylene (C13H10F12) derivatives with remarkable static and dynamic NLO response

Herein, based on density functional theory (DFT) simulations, the static and dynamic hyperpolarizabilities of the superalkalides based on Janus molecules have been explored. The designed superalkalides M2F(F)-DDFP-M2F(H) contain Janus based Dodecafluorophenylene (DDFP) molecule doped with superalkalis on both sides acting as both electron acceptors and donors. Thermodynamic stabilities are evident from the negative values of interaction energies, which are observed in the range of −2.96 eV to −3.63 eV. The maximum interaction energy (Eint) obtained is −3.63 eV for Li2F(F)-DDFP-Li2F(H) complex. The NBO (natural bond orbital) and FMO (frontier molecular orbital) analyses confirm the true superalkalide nature of the designed complexes. FMO analysis further reveals the reduction in energy gap E(H-L) from 10.43 eV (for bare DDFP) to 3.17 eV for the designed superalkalis. Furthermore, NLO response of the studied complexes reveals that the maximum values of polarizability (617 au) and hyperpolarizability are seen for Na2F(F)-DDFP-K2F(H) (4.25 × 104 au) complex, which confirms the remarkable NLO response of newly designed superalkalides. Moreover, frequency dependent analysis indicates that the maximum values of simple harmonic generation (SHG), electro-optical pockel effect (EOPE) and hyper Rayleigh scattering are 7.79 × 106, 2.75 × 106 and 4.45 × 106 au, respectively. The EOKE and EFISHG values are 6.79 × 107 and 7.68 × 1010 at 1339 nm suggesting significant increase in the NLO response of the reported complexes. These results manifest that our designed complexes might provide new paths towards the exceptionally high performance NLO materials. Moreover, we expect that the present work will provide guidance for designing and synthesis of superalkali based NLO materials in future.

Nanoimprinting Solution-Derived Barium Titanate for Electro-Optic Metasurfaces.

Electro-optic metasurfaces have demonstrated significant potential in enhancing the modulation speed and efficiency for fast and large-scale free-space optical devices. Barium titanate has a strong electro-optic Pockels coefficient, but its availability in thin-film form is restricted due to costly growth processes or low thickness. Here, we fabricated active metasurfaces using an etch-free bottom-up process with sol-gel-based polycrystalline barium titanate with a large electro-optic coefficient similar to bulk lithium niobate. We achieve strong hybrid Mie/surface lattice resonances with a quality-factor of 200 at 633 nm wavelength, enhancing the light-matter interaction and therefore the Pockels effect. The metasurface transmission is electro-optically modulated with up to 5 MHz driving frequency at low voltages of less than 1 V thanks to resonant enhancement of the modulation amplitude by 2 orders of magnitude. This successful demonstration of electro-optic modulation in nanoimprinted barium titanate structures paves the way for low-cost and large-scale free-space modulators or tunable metalenses.

Polarization-insensitive wide-angle resonant acousto-optic phase modulator.

Phase modulators are commonly used devices in optics. Free-space phase modulators are typically constructed from optically anisotropic crystals exhibiting the Pockels effect. To preserve the light's polarization state as it propagates through the crystal, it is essential to align the polarization and the angle of incidence of the light with respect to the crystal. In this study, we demonstrate the feasibility of constructing free-space resonant phase modulators with a broad acceptance angle and minimal dependence on the polarization state of light using an acousto-optic approach. These modulators operate in the megahertz frequency range, require modest power levels, have aperture sizes exceeding 1 cm2, and feature sub-millimeter thickness.

Development of optical voltage transformer using electro-optic Pockels effect for HVDC transmission systems

Development of optical voltage transformer using electro-optic Pockels effect for HVDC transmission systems

Simultaneous measurement of electrical potential on both sides of the dielectric surface in a parallel-plate dielectric barrier discharges and analysis of net electric field

Dielectric barrier discharges (DBDs) are widely used for ozone generation and surface treatment owing to their ability to generate reactive species. Surface charges generated during discharges distort the electric field between the dielectrics and affect the generation of reactive species. Therefore, the net electric field variations are of significant interest. Herein, a DBD measurement system for the net electric field based on the Pockels effect is established for the first time. The proposed system can simultaneously measure the surface potentials on both sides of the dielectric, thereby obtaining the net electric field at the discharge gap. The net electric field distribution varies insignificantly with the magnitude of the applied voltage but significantly with gap length. Moreover, the breakdown electric field increases with a decreasing gap length. This study provides a physical explanation for microgap reactors, demonstrating that the electric field in a DBD can be manipulated.

Lock-In Free ATR Detections of Organic Thin Film Pockels Effects within and beyond Nyquist

Lock-In Free ATR Detections of Organic Thin Film Pockels Effects within and beyond Nyquist

Polaron Formation in Conducting Polymers: A Novel Approach to Designing Materials with a Larger NLO Response.

Substantial efforts have been made to design and investigate new approaches for high-performance nonlinear optical (NLO) materials. Herein, we report polaron formation in conducting polymers as a new approach to designing materials with a large NLO response. A comparative study of polypyrrole and polypyrrole-based polaron (nPy+ where n = 1, 3, 5, 7, and 9) is carried out for optoelectronic and NLO properties. The studied polarons (PPy+) show excellent electronic properties and have reduced ionization potential (IP) as compared to neutral PPy, and a monotonic decrease is observed with increased chain lengths (1Py to 9Py). Interesting trends of global reactivity descriptors can be seen; the softness (S) increases with an increase in the chain length of PPy, while the hardness (η) decreases in the same fashion. The EH-L gaps for the PPy+ polaronic state are significantly lower than their corresponding neutral PPy. In the polaronic model (PPy+), radicals decisively reduce the crucial excitation energy, reminiscent of excess electrons (alkali metals). The performed TDOS spectral analysis further justifies the better conductive and electronic properties of polarons (PPy+) with increased chain lengths (conjugation). The static hyperpolarizability response (βo) is recorded up to 1.3 × 102 au for 9Py, while for polaron 9Py+, it has increased up to 3.2 × 104 au. The static hyperpolarizability of the 9Py+ polaronic state is 246 times higher than that of the corresponding neutral analogue, 9Py. It is observed that the values of βo obtained at the CAM-B3LYP/6-311+G(d,p) level of theory are comparable to those obtained at the LC-BLYP and ωB97XD functionals. The βvec values show a strong correlation with the total hyperpolarizability (βo). Furthermore, the calculated second harmonic generation (SHG) values are up to 4.0 × 106 au at 532 nm, whereas electro-optic Pockel's effect (EOPE) is much more pronounced at the smaller dispersion frequency (1064 nm). The TD-DFT study reveal the red-shifted absorption maxima (λmax) with an increased length of PPy+. A significant reduction in excitation energy (ΔE) is observed with increased length of PPy and PPy+, which also favors the improved NLO response. Hence, the studied thermally conducting polypyrrole-based polarons (PPy+) are new entries into NLO materials with better electrical and optical features.

Pockels Effect of Interfacial Water on a Mono-Electrode Induced by Current Parallel to the Electrode Surface

When an electric field is applied between two electrodes facing each other immersed in a liquid, the interfacial Pockels effect, a refractive index change proportional to the electric field, occurs in the electric double layer at the liquid–electrode interface. Here, we report that the Pockels effect of interfacial water can be observed even when an electric field is applied parallel to the surface of a “single” electrode in an electrolyte solution. This is a non-trivial result since the electric field parallel to the interface should not cause a broken spatial inversion symmetry, which is required for the Pockels effect. The Pockels signal was detected as a change in the transmitted light intensity due to the field-induced spectral shift of the interference fringes of the transparent conductive oxide electrode layer on a glass substrate. The magnitude of the signal increased as it approached the ends of the electrode, and the sign reversed across the center of the electrode. The electric field distribution calculated from the interfacial potential difference due to the in-plane parallel current showed that an electric field perpendicular to the interface was induced, whose distribution was consistent with the position dependence of the Pockels signal. A similar phenomenon was also observed for a single copper electrode, confirming that this is a universal effect.

Doping Induced Optical Band Gap Modification of Potassium Dihydrogen Phosphate

Aim: Potassium dihydrogen phosphate (KDP) is an excellent nonlinear optical material that has many potential applications, such as laser frequency conversion, Qswitches, Pockels cells, 3-D optical data storage devices, etc. Doping enhances various optical parameters of KDP. Doping changes in the absorbance and dopants such as aspartic acid, succinic acid, glycine, and L-alanine improved the optical band gap of the sample. Background: KDP is a non-linear optic material that has many important applications. Many researchers all over the world are trying to improve its optical properties. Objective: To synthesise pure KDP and KDP doped with aspartic acid, succinic acid, glycine, and L-alanine. Also, to study the temperature stability of the grown samples using TGA, DTA, and DSC analysis, Method: Growth from solution at low temperatures is used for the growth of crystals. TGA, DTA, and DSC are used to analyse the stability of the samples against temperature variations. Results: KDP crystals of good quality were grown using the slow cooling solution growth technique. Determined their band gap using the Tauc Plot. Significant variations in the optical bandgap are noticed. Also, the TGA, DTA, and DSC characterizations were done. Conclusion: KDP solution and grown crystals of good quality were synthesized. The variation in the bandgap on doping is a significant result as the modifications in bandgap enable the sample to be used in a more enhanced applications. Also, the doped samples were stable for variations in temperature, like the pure KDP.

Electric field mapping by Pockels effect and I(V) characteristic of CdTe nuclear detectors by different Pt contact deposition

In this work, we present the optimized principal methods of surface cleaning and treatment for CdTe nuclear detectors, namely: powder lapping, polishing and chemical etching mainly by Br- Methanol. We have studied the electric field mapping by Pockels effect technique. We made a comparison between the three main methods of Pt contact deposition: molecular beam epitaxy, cathode sputtering and the electroless (autocatalytic) methods in term of I(V) characteristic and electric field mapping. The two first method show: i) quite high uniform electric field, ii) the characteristic I(V) is non-uniform, iii) the detection suffer from the polarization effect. The I (V) characteristic shows that the contact is not ohmic. It is in the reversible I ∼ Vn with n varying from 0.643 to 1.651. The optimized contact deposit by electroless technique seems to be the more suitable one for detection with 2.10−8 A current at 200 V, a quite high uniform electric field up to 7 kV/cm, an absence of polarization effect and a spectrometric quality of nuclear detection.

Экспериментальные исследования свойств сверхтонких пленок ниобата лития методами зондовой и электронной микроскопии

The article is dedicated to the study of the physical and chemical properties of lithium niobate films made under different temperature conditions. Lithium niobate has already found its application in optics and has enormous potential in various technologies due to the emergence of effects such as piezoelectric effect, nonlinear optical effects, photoelasticity effect, and the Pockels effect (liner electro-optical effect). Lithium niobate can also be used in the oil industry as a catalyst for hydrogenation and dehydrogenation processes, hydrocracking, hydrodesulfurization, and hydroprocessing of oil and petroleum products due to its high surface activity, acidity, and thermal stability, as well as its ability to form stable dispersions in liquid media. The studies were cariied out using scanning electron microscopy technigues, scanning electron microscopy techniques, scanning electron microscopy to study the surface morphology of samples, Kelvin probe microscopy to measure the surface potential of the material, and piezoresponse force microscopy to register the piezoelectric effect of domain structures. As a result of the studies, scans of the surface morphology of samples were obtained, the electrical potential of the surface was measured, and the displacement of samples under the influence of an external elec-tric field with high resolution was also registered. The results of the study can be used to create new materials and devices with high performance and durability, as well as for further development of nanotechnology and nanoelectronics. Further research is planned to investigate other properties of lithium niobate films.

Tunable and stable micro-ring resonator based on thin-film lithium tantalate

As ferroelectric materials, lithium tantalate and lithium niobate share similar material characteristics, such as a high Pockels effect and nonlinear optical coefficients. When compared to lithium niobate, lithium tantalate offers a higher optical damage threshold, a broader transparent window, and lower birefringence, making it a promising candidate for high-performance electro-optical photonic integrated devices. In this study, we design and successfully fabricate micro-ring resonators on an acoustic-grade lithium-tantalate-on-insulator wafer, demonstrating their tunability and dynamic modulation capabilities. Experimental results indicate that the achieved thin-film lithium tantalate based micro-ring resonator exhibits an intrinsic Q-factor of 8.4 × 105, corresponding to a waveguide propagation loss of 0.47 dB/cm and a tuning efficiency of 1.94 pm/V. More importantly, as compared to those based on thin-film lithium niobate, a much weaker photorefractive effect and drift phenomenon around the 1550 nm wavelength under a direct-current drive are observed in the present fabricated thin-film lithium tantalate micro-rings with a silicon oxide over-cladding and a tuning electrode on top.

Linear electro-optic effect in strontium barium niobate: A first principles study

We report a first-principles study of the linear electro-optic or Pockels effect in SrxBa1-xNb2O6 (SBN). SBN is an attractive material for building electro-optic modulators in silicon photonics as it has one of the highest known Pockels coefficients and can be integrated on Si. We investigate the microscopic mechanism behind the giant Pockels effect and find that the optical phonon contribution dominates the electro-optic response. We identify the phonon modes that have a significant contribution to the Pockels response and discuss the microscopic origin of the response. In addition, we analyze the contribution of the converse piezoelectric effect to the Pockels response. We find good agreement when comparing our results to available experiment.

Modulation of electrodes on the sensitivity of the Pockels effect

In order to improve the sensitivity of the system in the Pockels effect, a design scheme for adding antennas at both ends of the crystal is proposed. Firstly, the influence of the applied electric field on the refractive index of the crystal is explored, and the relationship between the applied electric field and the output of the system is deduced. Secondly, two different antenna models are designed (one is to connect the antenna directly to both ends of the crystal, and the other is to connect the antenna after coating on the crystal), the distribution of the applied electric field in the internal field of the crystal under different models is studied, and the corresponding input and output transfer functions are analyzed. The analysis shows that the sensitivity of the system is improved in different antenna modes, and the crystal coating has little effect on the sensitivity. In addition, the antenna model without coating is simple to install, but the internal field strength of the crystal shows a tendency to be large in the middle and small at both ends, so it is easier to produce electric field breakdown effect in the strong field. The internal field strength distribution of the coated crystal is approximately uniform field, and the field strength maximum is smaller than that of the non-coated antenna model, so crystal breakdown is not easy to occur in the strong field. Finally, the effectiveness of the theoretical analysis is verified by experiments.