Pockels Effect Research Articles

Fiber electric double-layer platform for a phase shifter based on the Pockels effect of liquid molecules.

The electric double layer (EDL) was formed at the interface of the electrode and liquid and has been widely used in a series of applications, ranging from batteries to biosensors, based on the electrical property changes. In this paper, we demonstrate a simple microfiber phase shifter based on the Pockels effect of liquid in the electric double layer. By constructing an EDL around the microfiber, the phase shifter can be achieved. Furthermore, the effects of ion concentration and molecular polarity of liquids on this phase shifter were studied. The fiber electric double-layer platform has the advantages of low voltage modulation and simple fabrication, which has the potential for use in wearable sensing devices, biopotential detection, and biomolecule detection.

Pulse Picking PIV: A Single-Cavity Fiber Laser System For Highly Flexible Repetition Rates And Pulsing Schemes

A novel single-cavity laser system with flexible pulsing schemes suitable for particle image velocimetry (PIV) measurements is presented. The system is based on the concept of picking selected pulse pairs from an ultra-high repetition rate fiber laser which enables time-resolved and conventional dual-pulse PIV at highly flexible recording frame rates. Pulse picking PIV laser systems allow for the use of high-quality low speed dual-frame PIV cameras as well as highspeed cameras in both dual-frame and continuous recording modes, enabling the investigation of highly-transient phenomena at limited fields of view using time-resolved PIV as well as statistical PIV measurements with larger fields of view and higher spatial resolutions. The single-cavity output additionally avoids the alignment of laser beams of laser pulses, which is otherwise necessary in conventional dual-cavity PIV laser systems. Two pulse picking systems were set up and tested: An acousto-optic deflector selecting pulses using the diffraction across an acoustic wave and an electro-optic modulator rotating the polarization state of selected pulses in a Pockels cell. The performance of both systems was evaluated in terms of achievable inter-pulse durations, beam profile alterations, and pulse energy losses caused by the introduction of additional optical elements in the beam path.

Electro‐Optic Effect of ZnO Microcavity and Active Dynamic Lasing Mode Modulation

AbstractElectro‐optic effect, as a physical effect of electric field modulating refractive index, is widely applied to modulate lasing modes dynamically. However, the modulation is operated passively in general. It means that the lasing is generated in a resonance cavity and the modes are regulated externally in different materials and spaces. It will be highly favorable for optoelectronic integration and other applications when a gain medium with electro‐optic effect is applied to design an optical microcavity, integrating optical pumping and electro‐optic modulation. In this work, a hexagonal ZnO microrod is pumped optically to generate UV lasing with an electric field applied to modulate dynamically the resonance wavelength. When the electric field is parallel to the ZnO C‐axis, the refractive index variation is correlated linearly with the electric field strength (Pockels effect). When the electric field is perpendicular to the ZnO C‐axis, the refractive index variation shows a quadratic increase tendency with the increase of the electric field strength (Kerr electro‐optic effect). The whispering‐gallery lasing modes are dynamically modulated by applying an electric field successfully. In one word, lasing generation and modulation are integrated in the same microcavity based on both 1st and 2nd order electro‐optic effect.

An alternating approach of using multi-passing technique for development of massive phase difference between two orthogonal components of light in an electro-optic Pockels cell

An alternating approach of using multi-passing technique for development of massive phase difference between two orthogonal components of light in an electro-optic Pockels cell

Lanthanum doped corannulenes with enhanced static and dynamic nonlinear optical properties: A first principle study

In this work, lanthanum doping on corannulene (C20H10) buckybowls has been explored for their geometrical, electronic and nonlinear optical (NLO) properties via DFT simulations. The interaction energies of −21.75 to −40.01 kcal/mol reflect that A-D complexes are thermodynamically stable. The HOMO-LUMO energy gaps of designed complexes are decreased significantly up to 48.92%. A maximum charge transfer of 1.452 |e| is observed for complex A as revealed by natural bond orbital analysis. Non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses have confirmed the presence of various interactions in the complexes. The complexes are transparent in UV–Visible region and absorption maxima fall near infrared region (1123–2032 nm). The highest nonlinear optical response in terms of first hyperpolarizability value of 5.08 × 104 au is observed for complex C. The hyper-Rayleigh scattering (βHRS) and frequency dependent hyperpolarizability coefficients including electro-optical Pockel's effect and second harmonic generation are also computed theoretically.

M@[12-crown-4] and M@[15-crown-5] where (M=Li, Na, and K); the very first examples of non-conventional one alkali metal-containing alkalides with remarkable static and dynamic NLO response

Excess electron compounds , such as alkalides, were shown to be promising nonlinear optical (NLO) materials with higher static and frequency-dependent nonlinearities. The intriguing alkalides are obtained after doping the alkali metals with crown ethers M@[12-crown-4] and M@[15-crown-5] (where M=Li, Na, and K). The studied complexes are thermodynamically stable and their interactions energies range from −66.51 to −3.51 kcal mol −1 . The geometric, electronic, and nonlinear optical properties are validated through density functional theory at the CAM-B3LYP/6-31+G(d,p) level of theory. The significant (negative) NBO charge present on alkali metals reveals their alkalide characteristics. Furthermore, reduced HOMO-LUMO gaps for the designed complexes show their excellent electronic and conductive properties. Being excess electron candidate the significant static first hyperpolarizability value increased up to 1.2 × 10 7 au where the β vec response recorded up to 1.1 × 10 7 au. The total hyperpolarizability nicely correlates with hyperpolarizability ( β tl ) which suggests their excellent NLO properties. Besides, the dynamic hyperpolarizability response for electro-optical pockel's effect β(-2ω;ω,0) increases up to 3.5 × 10 7 au at dispersion frequency of 1064 nm. The dynamic hyperpolarizability responses for SHG are much pronounced at the larger dispersion frequency. The dynamic second hyperpolarizability response for the dc-Kerr effect increases up to 6.4 × 10 9 au. The frequency-dependent NLO response of M@[12-crown-4] alkalides is slightly larger than those of M@[12-crown-4]. Moreover, the hyper Rayleigh scattering hyperpolarizability (β HRS ) value is calculated up to 3.4 × 10 6 au. • Single alkali metal based non-conventional alkalides are proposed as excess electron compounds. • These shows better thermodynamic stabilities and significant interactions energies for M@[15-crown-5] complexes. • The higher hyperpolarizability response for Li@[15-crown-5] rose up to 1.2 × 10 7 au. • The remarkable frequency-dependent NLO properties at ω = 1064 nm.

An investigation and analysis of plasmonic modulators: a review

Abstract Plasmonics is an emerging and very advantageous technology which provides high speed and tiny size devices for fulfilling the demand of today’s high-speed world. SPPs are the information carrying elements in plasmonics, which are capable of breaking the diffraction limit. Plasmonics technology has shown its application in uncountable nanophotonic applications like switching, filtering, light modulation, sensing and in many more fields. Modulators are the key components of integrated photonic system. Various modulators which work on different effects are discussed in this study for providing a universal idea of modulators to researchers. Some useful plasmonic active materials are also discussed which are used in most of plasmonic modulators and other active devices. Previously, many researchers have worked on many kinds of modulators and switches, which operate on different kind of operating principles. For providing an overview about plasmonic modulators, their classification and their operation, we have discussed the state of art of some previously introduced modulators and switches which operates on electro-refractive effects and include electro-optic effect, Pockels effect, free charge carrier dispersion effect, phase change effect, elasto-optic effect, magneto-optic effect, and thermo-optic effect. Instead of different effects used in plasmonic switches and modulators different active materials like liquid crystals, graphene, vanadium di-oxide, chalcogenides, polymers, indium tin oxide, bismuth ferrite, barium titanate, and lithium niobate are also explained with their properties. Additionally, we also compared modulators based on different effects in terms of their design characteristics and performances.

The role of surface charge and its decay in surface dielectric barrier discharges

The charge accumulation and decay in surface dielectric barrier discharges (SDBDs) driven by a sine AC voltage waveform (4 kHz) in combination with a nanosecond positive voltage pulse (300 ns, 20 Hz) is experimentally investigated based on a combination of the electro-optical Pockels effect and a high-speed camera. It is found that the accumulation of positive surface charge on the dielectric promotes the discharge in the negative half cycle of the applied AC voltage, whereas it inhibits the development of following new positive charge filaments. The decay of a single positive charge filament on the surface is a result of the neutralization by negative charges that originate either from the migration of negative surface charge (electrons) or the drift of free electrons from the volume above the surface towards the surface. This work aims to contribute to a better understanding of the evolution of surface charge and its effects in SDBDs.

All-optical method for measuring the electrical parameters of passive electronic elements with active use of Pockels cells

All-optical method for measuring the electrical parameters of passive electronic elements with active use of Pockels cells

Integrated silicon carbide electro-optic modulator

Owing to its attractive optical and electronic properties, silicon carbide is an emerging platform for integrated photonics. However an integral component of the platform is missing—an electro-optic modulator, a device which encodes electrical signals onto light. As a non-centrosymmetric crystal, silicon carbide exhibits the Pockels effect, yet a modulator has not been realized since the discovery of this effect more than three decades ago. Here we design, fabricate, and demonstrate a Pockels modulator in silicon carbide. Specifically, we realize a waveguide-integrated, small form-factor, gigahertz-bandwidth modulator that operates using complementary metal-oxide-semiconductor (CMOS)-level voltages on a thin film of silicon carbide on insulator. Our device is fabricated using a CMOS foundry compatible fabrication process and features no signal degradation, no presence of photorefractive effects, and stable operation at high optical intensities (913 kW/mm2), allowing for high optical signal-to-noise ratios for modern communications. Our work unites Pockels electro-optics with a CMOS foundry compatible platform in silicon carbide.

A voltage measurement method based on pockels effect for UHV AC transmission line overvoltage monitoring

A voltage measurement method based on pockels effect for UHV AC transmission line overvoltage monitoring

Shedding light on the second order nonlinear optical responses of commercially available acidic azo dyes for laser applications

Nonlinear optics is a field of immense scientific interest and research owing to its extensive applications in photonics and optoelectronics. NLO materials are crucial components of optical fibers, optical computing, data processing devices, optical sensors, optical modulators, high density optical storage devices, and ultra-fast optical switches. Herein, five commercially available azo dyes, Acid Orange 5, Acid Orange 61, Direct Red 111, Food Yellow 6 and Metanil Yellow are theoretically investigated for their electronic and nonlinear optical properties using density functional theory (DFT) methods. Each azo dye exhibits one alkaline and two acidic forms therefore, all three forms of these azo dyes are considered for calculations. FMO analysis shows reduced HOMO-LUMO energy gaps (Eg) for acidic forms as compared to alkaline forms. The lowest HOMO-LUMO energy gap of 2.54 eV is observed for AO61 AC I acidic form. Furthermore, the effect of protonation of the dyes on nonlinear optical (NLO) responses are thoroughly investigated. The results at CAM-B3LYP/6-311+G(d) show that the protonation brings significant increase in nonlinear optical response. The highest first hyperpolarizability is observed for DR111 AC II (βo = 2.6 × 104au). The lowest hyperpolarizability calculated for Acid Orange 61 is even greater than that of the prototype, p-nitroaniline (1.2 × 103au). TD-DFT calculations are also carried out to find first hyperpolarizabilities βo by using two-level-model. The variations in dipole moments and excitation energies are the decisive factors for the increased first hyperpolarizabilities. In order to find the practical applications of the dyes in the field of nonlinear optics, dynamic hyperpolarizabilities for hyper-Rayleigh scattering (HRS), second harmonic generation (SHG) and electro-optical Pockel's effect (EOPE) are computed at a varying range of incident wavelengths. The results are found to be quite supportive for application of the studied azo dyes in second harmonic generation phenomenon.

Propagation of the odd-Pearcey Gauss beam in the uniaxial crystals with the Pockels effect

In this paper, the propagation dynamics of an odd-Pearcey Gauss beam (OPGB) in uniaxial crystals along the optical axis governed by the Pockels effect is analytically and numerically investigated. In this case, the left-hand circularly polarized OPGB gives rise to the right-hand vortex component possessing a topological charge of 2. Results show that the focusing intensity, the focusing distance, the focal point size, the efficiency of the power exchange between these two contributions and the conversion between spin angular momentum (SAM) and orbit angular momentum (OAM) can be controlled by choosing an appropriate external electric field. Furthermore, the right-hand vortex component can be utilized to trap the nanoparticles whose refractive index is lower than that of the surroundings. The energy flow and the angular momentum of the OPGB are also studied. Particularly, with increasing the ratio of the extraordinary index to the ordinary index in a uniaxial medium, both two contributions perform bifocusing behavior.

Picosecond Pulsed-Periodic High-Peak Power Nd:YAG Laser Operationally Controlled by KTP-Based Pockels Cell

Electro-optical modulators are effectively used for ultrafast pulse lasers operation control. The scheme of picosecond pulse-periodic high-peak-power Nd:YAG lasers is composed of an active-passive mode-locked and negative feedback-controlled master oscillator and regenerative amplifier based on common end-diode-pumped Nd:YAG crystal. A double-crystal thermally compensated Pockels cell based on KTP crystals of the Y-cut direction is employed as a key control element. The cell was assembled using a pair of equal-length crystals grown according to high-resistivity technology. The scheme provides output pulses with energy up to 1.6 mJ, a duration of 25 ps at repetition rates tunable from 0 to 200 Hz. The laser operation stages are analyzed in detail. The scheme looks attractive and promising for developing advanced ultrafast laser systems with higher repetition rates, peak and, accordingly, average power levels. The Pockels cell based on KTP crystals expands the line of available fast electro-optical control elements, along with the previously used RTP ones. The factors limiting laser pulse energy and repetition rate are discussed. Parasitic nonlinear conversion in the crystals of the Pockels cell along the axis may play an essential role. The results of comparative measurements of the second and third harmonics made with the Pockels cells based on KTP and RTP crystals of both X-cut and Y-cut directions are presented. The minimum second and third harmonics efficiency levels observed in the Y-cut Pockels cells of the KTP crystal seem to be their important advantage.

Identification of Railway Power Supply Voltage Sag Source Using Optical Fiber Voltage Sensor

With the construction of the smart grid and the continuous improvement of voltage levels, the traditional voltage sensor can no longer meet the development needs of the modern power system. There is an urgent need for a new high-quality voltage sensor to replace it. Aiming at the problems of complex structure, difficult adjustment, poor temperature stability, large optical power loss and inconvenient voltage introduction of the existing optical fiber voltage sensor, an optical fiber voltage sensor based on full polarization state detection without polarizer and analyzer is proposed. The sensor only contains three main components: Grin Lens, BGO crystal and total reflection mirror. It has few devices, simple structure and easy alignment. Moreover, the polarization state evolution and high voltage on the transmission line of Pockels effect of BGO crystal are analyzed. The voltage sag simulation model of the electrified railway is established. The sample data of different disturbance sources are obtained with the assistance of the designed optical fiber voltage sensor. S-transformation and Radial Basis Function (RBF) neural networks are introduced and combined with the prototype of electrified railway power quality detection and analysis device to identify voltage sag sources. The designed optical fiber voltage sensor is suspended. There is no electrode or grounding on the sensor, which saves expensive insulators and increases the sensor’s measuring range. The sensor has a good linear relationship in the power frequency AC voltage range of 0~10 kV at room temperature. It is proved that the design is effective. The working condition analysis of the actual railway power supply reveals that it can detect the voltage sag amplitude and disturbance time, and identify the type of voltage sag disturbance source.

Interfacial Pockels Effect of Solvents with a Larger Static Dielectric Constant than Water and an Ionic Liquid on the Surface of a Transparent Oxide Electrode

The optical Pockels effect is a change in the refractive index proportional to an applied electric field. As a typical example of the interfacial Pockels effect occurring at interfaces where the spatial inversion symmetry is broken, it is known that water in the electric double layer (EDL) on the transparent oxide electrode surface has a large Pockels coefficient, but the physical factors that determine its size are not clear. Therefore, we experimentally studied the Pockels effect of water and other characteristic liquids—formamide (FA), methylformamide (NMF) (these two have larger static dielectric constants than water), dimethylformamide (DMF), and an ionic liquid that is itself salts (IL, [BMIM] [BF4])—and evaluated their Pockels coefficients in the EDL on the transparent electrode surface. The magnitude of the Pockels coefficient was found to be in the order of water, DMF, FA, NMF, and IL, with the magnitude of the static dielectric constant not being an important factor.

Optical Writing and Electro-Optic Imaging of Reversible Space Charges in Semi-Insulating CdTe Diodes.

Deep levels control the space charge in electrically compensated semi-insulating materials. They limit the performance of radiation detectors but their interaction with free carriers can be favorably exploited in these devices to manipulate the spatial distribution of the electric field by optical beams. By using semi-insulating CdTe diodes as a case study, our results show that optical doping functionalities are achieved. As such, a highly stable, flux-dependent, reversible and spatially localized space charge is induced by a line-shaped optical beam focused on the cathode contact area. Real-time non-invasive imaging of the electric field is obtained through the Pockels effect. A simple and convenient method to retrieve the two-dimensional electric field components is presented. Numerical simulations involving just one deep level responsible for the electrical compensation confirm the experimental findings and help to identify the underlying mechanism and critical parameters enabling the optical writing functionalities.

Design and stability analysis of broadband trsansient electric field sensor for new power system

Broadband transient voltage measurement is the most direct means to master the fault characteristics of new power system. In view of the fact that the traditional measurement method based on mutual inductance principle is limited by the measurement frequency band and cannot accurately measure the transient voltage, this paper designs and implements an integrated optical electric field sensor (IOES) based on Pockels effect, which has the characteristics of wide frequency band, strong antiinterference ability and good insulation, and takes the IOES as the core to form the electric field measurement system, The input and output characteristics of the electric field measurement system are given. In order to apply the IOES to the on-line monitoring of transient voltage, the stability of temperature and humidity of the electric field sensor is theoretically analyzed, and the measures to improve the stability are put forward.

Highly accurate DFT investigation for triggering the ultra-strong static and dynamic nonlinear optical properties of superalkali doped aminated graphdiyne (NH2-GDY) donor-π-acceptor (D-π-A) quantum dots

Keeping in mind the desirability of novel two-dimensional materials with an ultra-high nonlinear optical (NLO) response for the fabrication of optoelectronic devices, we have investigated nine complexes by doping superalkalis (M2X; M = Li, Na, K and X = F, Cl, Br) onto the novel aminated graphdiyne (NH2-GDY) quantum dots. The geometric, electronic and NLO responses (static and dynamic) of the M2X doped aminated graphdiyne (M2X@NH2-GDY) complexes have been systematically investigated using density functional theory (DFT) computations. All the superalkalis are preferably oriented on the triangular large porous site of NH2-GDY containing extensive delocalized π-conjugated electrons and interact via an intermolecular π-electron donor–acceptor (D-π-A) process. The lithium and potassium-containing superalkali doped complexes exhibit high structural stability due to their large interaction energies. The change in the electronic properties of the M2X doped NH2-GDY quantum dots is investigated by analyzing the NBO charge transfer, vertical ionization energies (VIEs), HOMO-LUMO energy gaps and density of states spectra. TD-DFT calculations show ultra-high transparency of these complexes in the ultraviolet region. The strong NLO characteristics of the designed complexes are demonstrated by their high static and dynamic hyperpolarizability values. Among all the nine complexes, the K2F@NH2-GDY, K2Cl@NH2-GDY and K2Br@NH2-GDY complexes possess exceptionally high βo values: 1.16 × 104, 1.06 × 104 and 1.02 × 104 au, respectively, owing to the large atomic radius and high atomic number of the potassium metal atoms. The frequency-dependent NLO responses, Electro-Optical Pockels Effects (EOPE) and Second Harmonic Generation (SHG) are analyzed to investigate the dynamic NLO response. It is revealed that the K2X@NH2-GDY complexes also exhibit exceptionally high dynamic NLO responses (107 or 108 au) at 1064 nm wavelength. Our present research not only highlights the significance of superalkali doping on aminated graphdiyne quantum dots but also indicates that the K2X@NH2-GDY complexes are potentially important for next-generation optoelectronic devices.

Superalkali (Li2F, Li3F) doped Al12N12 electrides with enhanced static, dynamic nonlinear optical responses and refractive indices

In the present work, superalkalis (Li2F and Li3F) doped Al12N12 nanocages have been designed and investigated theoretically to elucidate the correlations between geometric, electronic and nonlinear optical properties. All complexes (A-E) are stable inorganic electrides as indicated by their interaction energies (−52.97 to −87.58 kcal/mol). The decrease in HOMO-LUMO energy gaps (5.44–5.87 eV) has caused a remarkable increase in the nonlinear optical response of A-E complexes. The maximum values of first hyperpolarizability (1.20 × 104 a.u.) and second hyperpolarizability (1.65 × 107 a.u.) have been achieved for complex A. The highest dynamic hyperpolarizability coefficients including second harmonic generation (9.08 × 105 a.u.) and electro-optic Pockel's effect (9.56 × 105 a.u.) are obtained for complex A at 532 nm. The electric field-induced second harmonic generation (up to 3.52 × 108 a.u.) and dc-Kerr effect (up to 8.13 ×108 a.u.) along with a large quadratic nonlinear refractive index (up to 5.41 × 10−11 a.u.) of the designed electrides reflected their large NLO response.