Electro-optic Switch Research Articles

Electro-optic mode-selective switch based on cascaded three-dimensional lithium-niobate waveguide directional couplers

We propose an electro-optic mode-selective switch based on cascaded three-dimensional lithium-niobate waveguide directional couplers fabricated with a single-step annealed proton-exchange process. To compensate for discrepancies due to uncertainties in the fabrication process, we develop a post-tuning technique to improve the performance of the coupler by means of depositing a layer of titanium oxide (TiO2) onto one of the waveguides of the coupler. By integrating two cascaded dissimilar directional couplers, we experimentally demonstrate switchable (de)multiplexing of the LP01, LP11a, and LP11b modes, where the LP11a mode can be switched at an efficiency over 75% from 1530 nm to 1612 nm with an applied voltage varying between -9 V and +30 V, and the LP11b mode can be switched at an efficiency higher than 90% from 1534 nm to 1577 nm with an applied voltage varying between -21 V to 0 V. The switching times are 230-300 ns. Our proposed waveguide platform could be employed to develop advanced switches for applications in areas where high-speed switching of spatial modes is required, such as reconfigurable mode-division-multiplexing communication.

Electro-optical Performance Investigation of Cholesteric Liquid Crystal Containing Azo Dye: Light Shutter Device Application

In this study, the effect of chiral dopant concentration on electro-optical and dielectric properties of a cholesteric liquid crystal (CLC) composite was investigated, and a dye-doped cholesteric liquid crystal (DDCLC) light shutter was developed. The electro-optical properties of samples were investigated by electro-optical switching method without the use of a polarizer. The dielectric characterization of the composites were also realized using dielectric spectroscopy technique with a wide frequency range. Significant electro-optical and dielectric parameters, such as transition voltages, complex dielectric constant, dielectric anisotropy and light transmission values of composites were found from the experimental data. The obtained results show that the chiral dopant causes changes in electro-optical and dielectric parameters of CLC, and the developed DDCLC light shutter can be used in optoelectronic device applications.

Interaction potential function for the deformation analysis of potassium dihydrogen phosphate using molecular dynamics simulation

Potassium dihydrogen phosphate (KDP) is an important nonlinear optical material which plays a core role in electro-optic switches and laser spectroscopy. However, KDP is also one of the most difficult-to-handle materials due to its fragility, unstable microstructure and complex mechanical behaviour. Molecular dynamics (MD) simulation is an appropriate method to explore the deformation mechanisms of the material at the atomic scale. However, the challenge is that there is not a suitable potential function for describing the mechanical behaviour of KDP by using MD simulation. This paper successfully developed a potential function, which enables such insightful investigations. It was found that the established potential function can reliably predict the mechanical properties of KDP including its modulus in different crystal directions and structural changes under various loading conditions.

Antiferromagnetism-induced second-order nonlinear optical responses of centrosymmetric bilayer CrI3

Antiferromagnetism (AF) in AB′-stacked centrosymmetric bilayer (BL) CrI3 breaks both spatial inversion (P) and time-reversal (T) symmetries but maintains the combined PTsymmetry, thus inducing novel second-order nonlinear optical (NLO) responses such as second-harmonic generation (SHG), linear electric-optic effect (LEO) and bulk photovoltaic effect (BPVE). In this work, we calculate AF-induced NLO responses of the BL CrI3 based on the density functional theory with the generalized gradient approximation (GGA) plus onsite Coulomb correlation (U), i.e., the GGA+U method. Interestingly, we find that the magnetic SHG, LEO and photocurrent in the AF BL CrI3 are huge, being comparable or even larger than that of the well-known nonmagnetic noncentrosymmetric semiconductors. For example, the calculated SHG coefficients are in the same order of magnitude as that of MoS2 monolayer (ML), the most promising 2D material for NLO devices. The calculated LEO coefficients are almost three times larger than that of MoS2 ML. The calculated NLO photocurrent in the CrI3BL is among the largest values predicted so far for the BPVE materials. On the other hand, unlike nonmagnetic semiconductors, the NLO responses in the AF BL CrI3 are nonreciprocal and also switchable by rotating magnetization direction. Therefore, our interesting findings indicate that the AF BL CrI3 will not only provide a valuable platform for exploring new physics of low-dimensional magnetism but also have promising applications in magnetic NLO and LEO devices such as frequency conversion, electro-optical switches, and light signal modulators as well as high energy conversion efficiency photovoltaic solar cells.

Electro-Ionic Control of Surface Plasmons in Graphene-Layered Heterostructures.

Precise control of light is indispensable to modern optical communication devices especially as the size of such devices approaches the subwavelength scale. Plasmonic devices are suitable for the development of these optical devices due to the extreme field confinement and its ability to be controlled by tuning the carrier density at the metal/dielectric interface. Here, an electro-ionic controlled plasmonic device consisting of Au/graphene/ion-gel is demonstrated as an optical switch, where an external electric field modulates the real part of the electrical conductivity. The graphene layer enhances charge penetration and charge separation at the Au/graphene interface resulting in an increased photoinduced voltage. The ion-gel immobilized on the Au/graphene further enables the electrical tunability of plasmons which modulates the intensity of the reflected laser light. This work paves the way for developing novel plasmonic electro-optic switches for potential applications such as integrated optical devices.

An Optical Switch Based on Electro-Optic Mode Deflection in Lithium Niobate Waveguide

We propose a 1 × 2 electro-optic miniature optical switch based on mode deflection of lithium-niobate (LN) annealed proton exchange waveguides with microstructured electrodes. Our fabricated device consists of LN waveguides covered with isosceles-triangle-shaped array electrodes, a horn-shaped input waveguide, and two tapered output waveguides. At a driving voltage of 40 V, the two-modes can switch between two output ports with an extinction ratio of 17.39 dB at the wavelength of 1530 nm. The switching speed is 22 ns. This miniature mode switch could find applications in signal processing and high-speed optical communication networks.

Tunable twisted-mode Ho:YAG laser at continuous-wave and pulsed operation.

A single-longitudinal-mode Ho:YAG laser with a twisted-mode cavity under the continuous-wave and pulsed operation was demonstrated. The maximum continuous-wave single-longitudinal-mode output power of 0.76 W was obtained at the wavelength of 2097.46 nm, corresponding to a slope efficiency of 28.9%. The output wavelength was tuned from 2096.94 nm to 2098.48 nm by utilizing a 0.5-mm-thick etalon. Furthermore, the single-frequency pulsed operation of the twisted-mode Ho:YAG laser was realized by the electro-optic switch. For the 2 kHz pulse repetition frequency, the single-frequency pulse energy reached 0.2 mJ with the pulse width of 116.5 ns. The beam quality factors M2 of the pulsed twisted-mode Ho:YAG laser in the x and y directions were 1.15 and 1.10, respectively.

Amplitude modulation of radiation by coupled resonators

In this paper, we describe a method that allows one to realize highly efficient amplitude modulation of radiation at the output of electro-optical laser switches with two coupled resonators, in which electro-optical elements are located both in two split arms and in every arm of a multipath interferometer with combined channels with a control voltage 2 times lower than in existing laser switches. Moreover, the electro-optical elements located in the two split arms of a multipath interferometer with combined channels, with one passage of the light flux through the electro-optical element, must make the opposite controlled changes in the phase difference of the interfering light beams. Therefore, for such electro-optical switches with two coupled resonators the value of the required electric power will be, respectively, 2 times less than that of the existing ones, which significantly expands their operating frequency range. In this case, a laser switch with electrooptical elements located in the two split arms of a multipath interferometer has an asymmetric dependence of the output radiation intensity on the change in the phase difference of the interfering light beams relative to the zero value of the light intensity. A laser switch with electro-optical elements located on all arms of a multipath interferometer with combined channels has a symmetric dependence of the output radiation intensity on the magnitude of the phase difference of the interfering light beams relative to the zero value of the light intensity. In addition, due to the coherent summation of the amplitudes of the interfering light waves, such laser electro-optical shutters also have amplification of radiation with a resonant wavelength.

Fast Mode in the Electro-Optical Switching of a Liquid Crystal Cell with Interdigitated Electrodes

The conditions for the emergence of a fast electro-optical mode in a liquid crystal cell with a short period (p = 1.8 μm) of interdigitated electrodes have been investigated. The electro-optical switching in two liquid crystal mixtures differing in viscosity and dielectric and optical anisotropies has been studied through numerical simulations and experimentally. The fast mode switching times are shown to be in the submillisecond range and to be related to the switching of a near-electrode liquid crystal layer comparable in thickness to the period of the electrode structures. The inclusion of the entire liquid crystal volume in the switching process is characterized by a slow mode with considerably longer times.

Tunable THz and Infrared Plasmonic Filters and Switches Based on Circular Graphene Resonator With 90$^\circ$ Bending of Output Port

Two types of novel graphene-based components, namely, filters and electro-optical switches in guided wave configuration are suggested and analysed. The filters differ from the known ones with collinear orientation of the input and output waveguides by geometry and symmetry. The components consist of a circular graphene disk and two nanoribbons oriented at 90° to each other in the plane of the graphene layer. The graphene elements are placed on a dielectric substrate. We show that change in symmetry leads to a drastic change in the properties of the components. The physical principle of the devices is based on the dipole, quadrupole and hexapole resonances in the graphene disk which define stop-band, pass-band and stop-band frequency characteristics, respectively. A combination of stop-band and pass-band filter properties by shifing the electronic Fermi level allows one to design a switch. Numerical simulations show that the suggested components have very small dimensions, good characteristics and provide a dynamic control of their central frequency via electrostatic gating.

Narrowband perfect metasurface absorber based on impedance matching

We presented a numerical investigation of a metamaterial narrowband perfect absorber conducted via a finite element method based on commercially available COMSOL software. The periodic array of silicon meta-atoms (MAs) are placed on 80 nm thick gold layer. The broadband light at normal incidence is blocked by the gold layer and silicon MAs are used to excite the surface plasmon by scattering light through it. Maximum absorption of 95.7 % is obtained at the resonance wavelength of 1137.5 nm due to the perfect impedance matching of the electric and magnetic dipoles. The absorption is insensitive to the wide-angle of incidence ranging from 0 to 80 degrees. We believe that the proposed metamaterial device can be utilized in solar photovoltaic and biochemical sensing applications. Full Text: PDF ReferencesY. Cheng, X.S. Mao, C. Wu, L. Wu, R.Z. Gong, "Infrared non-planar plasmonic perfect absorber for enhanced sensitive refractive index sensing", Optical Materials, 53, 195-200 (2016). CrossRef S. S. Mirshafieyan, D.A. Gregory, "Electrically tunable perfect light absorbers as color filters and modulators", Scientific Reports,8, 2635 (2018). CrossRef D.M. Nguyen, D. Lee, J. Rho, "Control of light absorbance using plasmonic grating based perfect absorber at visible and near-infrared wavelengths", Scientific Reports, 7, 2611 (2017). CrossRef Y. Sun, Y. Ling, T. Liu, L. Huang, "Electro-optical switch based on continuous metasurface embedded in Si substrate", AIP Advances, 5, 117221 (2015). CrossRef H. Chu, Q. Li, B. Liu, J. Luo, S. Sun, Z. H. Hang, L. Zhou, Y. Lai, "A hybrid invisibility cloak based on integration of transparent metasurfaces and zero-index materials", Light: Science & Applications, 7, 50 (2018). CrossRef S. K. Patel, S. Charola, J. Parmar, M. Ladumor, "Broadband metasurface solar absorber in the visible and near-infrared region", Materials Research Express, 6, 086213 (2019). CrossRef Q. Qian, S. Ti, C. Wang, "All-dielectric ultra-thin metasurface angular filter", Optics Letters, 44, 3984 (2019). CrossRef P. Yu et al., "Broadband Metamaterial Absorbers", Advanced Optical Materials, 7, 1800995 (2019). CrossRef Y. J. Kim et al., "Flexible ultrathin metamaterial absorber for wide frequency band, based on conductive fibers", Science and Technology of advanced materials, 19, 711-717 (2018). CrossRef N.L. Kazanskiy, S.N. Khonina, M.A. Butt, "Plasmonic sensors based on Metal-insulator-metal waveguides for refractive index sensing applications: A brief review", Physica E, 117, 113798 (2020). CrossRef H. E. Nejad, A. Mir, A. Farmani, "Supersensitive and Tunable Nano-Biosensor for Cancer Detection", IEEE Sensors Journal, 19, 4874-4881 (2019). CrossRef

Lithium niobate photonic-crystal electro-optic modulator

Modern advanced photonic integrated circuits require dense integration of high-speed electro-optic functional elements on a compact chip that consumes only moderate power. Energy efficiency, operation speed, and device dimension are thus crucial metrics underlying almost all current developments of photonic signal processing units. Recently, thin-film lithium niobate (LN) emerges as a promising platform for photonic integrated circuits. Here, we make an important step towards miniaturizing functional components on this platform, reporting high-speed LN electro-optic modulators, based upon photonic crystal nanobeam resonators. The devices exhibit a significant tuning efficiency up to 1.98 GHz V−1, a broad modulation bandwidth of 17.5 GHz, while with a tiny electro-optic modal volume of only 0.58 μm3. The modulators enable efficient electro-optic driving of high-Q photonic cavity modes in both adiabatic and non-adiabatic regimes, and allow us to achieve electro-optic switching at 11 Gb s−1 with a bit-switching energy as low as 22 fJ. The demonstration of energy efficient and high-speed electro-optic modulation at the wavelength scale paves a crucial foundation for realizing large-scale LN photonic integrated circuits that are of immense importance for broad applications in data communication, microwave photonics, and quantum photonics.

Electric field controlled near-infrared high-speed electro-optic switching modulator integrated with 2D MgO.

The electro-optic effect in two-dimensional (2D) MgO nanoflakes synthesized by a microwave-assisted process is demonstrated using a designed optical fiber modulator. The guiding properties of intense core modes excited by the material cavity are modulated by the external electric field. The feasibility of 2D MgO nanoflakes as an effective electro-optic modulator and switching are experimentally verified for the first time, to the best of our knowledge. The proposed optical-fiber-based electro-optic modulator achieves a linear wavelength shift with a high sensitivity of 12.87 pm/V(77.22 nm/kV/mm, in the electric field). The results show that MgO, as a metal oxide 2D material, is a very promising material for electro-optic modulators and switching.

A superfast responsive and ultrathin self-constructed bilayer nanoarchitecture for automatic vertical orientation of liquid crystals

Ultrathin bilayer nanoarchitectures are structurally and functionally tunable yet robust, which are hierarchical building blocks with a wide range of applications from flexible displays to wearable optoelectronic devices. Here, we report an unprecedented cost-effective fabrication strategy to construct an ultrathin, superfast responsive, and highly durable bilayer nanoarchitecture for automatic vertical arrangement of liquid crystals (LCs) by using the spontaneous and cooperative self-construction of small mesogenic amphiphiles. The self-constructed bilayer nanoarchitecture is achieved by the simple doping and subsequent in situ self-assembly of a small amount of mesogenic amphiphiles in the confined cell geometry. It is experimentally demonstrated that an ultrathin and rough bilayer nanoarchitecture with vertical nanopillar array formed by surficial hydrogen bonding and cooperative π–π interaction of mesogenic amphiphiles enables an automatic vertical orientation of LC molecules to be realized during self-construction process. In addition, this simple approach provides a superfast responsive and highly reliable nanoarchitecture with a greatly enhanced electro-optical switching performance compared to conventional polyimide alignment layer. The ultrafast response time of 1.5 ms, which is more than ten times faster than that obtained from a conventional alignment layer, and low voltage driving achieving about 33% energy savings are accomplished by our method.

N x N x Mλ electro-optical nanobeam wavelength-multiplexed cross-connect switches using push-push addressing.

In this theoretical work, we design elemental and higher-order wavelength-division-multiplexed cross-connects (WXCs): nonblocking space-and-wavelength routing switches to be constructed in a monolithic, industry-standard, silicon-on-insulator (SOI) chip operating at a center wavelength of 1550 nm. Each multi-spectral multi-crossbar 2×2 x Mλ "element" of the network switch is an M-fold cascade connection of λ-diverse SOI Mach-Zehnder interferometers (MZIs), each of which utilizes a nanobeam cavity in each MZI arm. Within the element, each MZI has an electro-optically (EO) controlled local PN-junction "depleter" embedded in each cavity. The cavity voltage commands are (0,0) or (V,V) where V is a "small" reverse bias. Each element can be reconfigured in 2 to 5 ps, depending on Q, with few-fJ/bit switching energy. For the M = 3 case, a compact 6-element 4×4×3λ WXC is presented. In addition, compact new designs are given for a 12-element 8×8×3λ WXC and for 16×16×8λ WXCs employing either 56 or 72 elements.

Electrical Characterization of E7 Liquid Crystal Molecules under the Impact of an External Electric Field (THz): A Theoretical approach

In this work, different parameters of E7 liquid crystal (LC) have been calculated under the influence of an electric field in THz frequency. The E7 LC parameters have positive as well as negative values of order parameter and birefringence under the influence for an electric field. The director angle of E7 LC shows fast fluctuations above the angle θ=45° and due to rapid change in the orientation of molecules, fast electro-optical switching devices based on E7 LC can be designed. The refractive index of the E7 LC maintains stability in THz frequency.

Tunable Electro- and All-Optical Switch Based on Epsilon-Near-Zero Metasurface

A novel design of a tunable optical switch based on epsilon-near-zero (ENZ) metasurface is proposed, which can work as an electro-optical or an all-optical switch, and be tuned by gate-voltages, incident angles, and intensity of pump light. The result shows that the coupling of the ENZ mode and plasmon resonance lead to an obvious Rabi splitting which can be observed in the transmission spectrum. Numerical analysis also demonstrates that the coupling belongs to the ultra-strong coupling regime. The proposed design can achieve electro-optical switching with a large modulation depth of up to ∼ 17 dB, all-optical switching with an extinction ratio exceeding 5 dB and an ultrafast response time of 650 fs.

Self-Assembling Behavior of Smart Nanocomposite System: Ferroelectric Liquid Crystal Confined by Stretched Porous Polyethylene Film.

The control and prediction of soft systems exhibiting self-organization behavior can be realized by different means but still remains a highlighted task. Novel advanced nanocomposite system has been designed by filling of a stretched porous polyethylene (PE) film with pore dimensions of hundreds of nanometers by chiral ferroelectric liquid crystalline (LC) compound possessing polar self-assembling behavior. Lactic acid derivative exhibiting the paraelectric orthogonal smectic A* and the ferroelectric tilted smectic C* phases over a broad temperature range is used as a self-assembling compound. The morphology of nanocomposite film has been checked by Atomic Force Microscopy (AFM). The designed nanocomposite has been studied by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), small and wide-angle X-ray scattering and broadband dielectric spectroscopy. The effect of a porous PE confinement on self-assembling, structural, and dielectric behavior of the chiral LC compound has been established and discussed. While the mesomorphic and structural properties of the nanocomposite are found not to be much influenced in comparison to that of a pure LC compound, the polar properties have been toughly suppressed by the specific confinement. Nevertheless, the electro-optic switching was clearly observed under applied electric field of low frequency (210 V, 19 Hz). The dielectric spectroscopy and X-ray results reveal that the helical structure of the ferroelectric liquid crystal inside the PE matrix is completely unwound, and the molecules are aligned along stretching direction. Obtained results demonstrate possibilities of using stretched porous polyolefins as promising matrices for the design of new nanocomposites.

Modeling and Performance Enhancement of Active Hybrid Plasmonic Electro-optic Routing Switch

This paper produces a more compact and efficient design for hybrid plasmonic 2 × 2 electro-optic routing switch, with aid of an active material that has an electrically tunable permittivity, and discusses its ability for realizing more advanced structures. The proposed 2 × 2 electro-optic switch, with foot print of 11.6 μm2 and switching time of 0.949 pS, satisfies transmission values (coupling efficiency) less than 7% at OFF state and greater than 75% at ON state at the telecommunication wavelength. This design is used as a base unit to realize two advanced structures: (a) the 3 × 3 switching matrix, with a foot print of 47–49 μm2, which satisfies transmission greater than 60% at ON states and transmission less than 10% at OFF states, and (b) the 4 × 4 switching matrix, with a foot print of 88 μm2, which satisfies transmission greater than 70% at ON states and transmission less than 5% at OFF states. The obtained results have a validation with older researches. A 3D finite-difference time-domain (FDTD) solver is employed to simulate and characterize the realized structures. The components would be useful in the optical interconnect networks, photonic integrated circuits, and signal processing system.

An integrated optical modulator operating at cryogenic temperatures.

Photonic integrated circuits (PICs) operating at cryogenic temperatures are fundamental building blocks required to achieve scalable quantum computing and cryogenic computing technologies1,2. Silicon PICs have matured for room-temperature applications, but their cryogenic performance is limited by the absence of efficient low-temperature electro-optic modulation. Here we demonstrate electro-optic switching and modulation from room temperature down to 4 K by using the Pockels effect in integrated barium titanate (BaTiO3) devices3. We investigate the temperature dependence of the nonlinear optical properties of BaTiO3, showing an effective Pockels coefficient of 200 pm V-1 at 4 K. The fabricated devices show an electro-optic bandwidth of 30 GHz, ultralow-power tuning that is 109 times more efficient than thermal tuning, and high-speed data modulation at 20 Gbps. Our results demonstrate a missing component for cryogenic PICs, removing major roadblocks for the realization of cryogenic-compatible systems in the field of quantum computing, supercomputing and sensing, and for interfacing those systems with instrumentation at room temperature.