Electro-optic Switch Research Articles

Dual-mode 2 × 2 electro-optic switch on a SOI platform.

Mode-division multiplexing (MDM) technology is promising for enhancing the capacity of communication networks. In this Letter, we demonstrate a dual-mode 2 × 2 electro-optical switch on a silicon-on-insulator platform. The dual-mode Mach-Zehnder interferometer switch comprises of four p-i-n phase shifters and two mode-insensitive multimode interferences that can be used for TE0 and TE1, simultaneously. With π/2 phase shifters introduced, push-pull like operation enables the power consumption lower than 2.15 mW. The average insertion loss of the switch in "cross" and "bar" states are 1.31 dB ± 0.19 dB for the TE0 mode and 3.39 dB ± 0.16 dB for the TE1 mode, respectively. The cross talk is less than -16.47 dB in the C band. The compact dual-mode switch is promising to conduct a large-scale, flexible MDM system on chip.

Microsecond electro-optic switching in the nematic phase of a ferroelectric nematic liquid crystal

Microsecond electro-optic switching in the nematic phase of a ferroelectric nematic liquid crystal

Reverse Mode Polymer Stabilized Cholesteric Liquid Crystal Flexible Films with Excellent Bending Resistance.

The reverse-mode smart windows, which usually fabricated by polymer stabilized liquid crystal (PSLC), are more practical for scenarios where high transparency is a priority for most of the time. However, the polymer stabilized cholesteric liquid crystal (PSCLC) film exhibits poor spacing stability due to the mobility of CLC molecules during the bending deformation. In this work, a reverse-mode PSCLC flexible film with excellent bending resistance was fabricated by the construction of polymer spacer columns. The effect of the concentration of the polymerizable monomer C6M and chiral dopant R811 on the electro-optical properties and polymer microstructure of the film were studied. The sample B2 containing 3 wt% of C6M and 3 wt% R811 presented the best electro-optical performance. The electrical switch between transparent and opaque state of the flexible PSCLC film after bending not only indicated the excellent electro-optical switching performance, but also demonstrated the outstanding bending resistance of the sample with polymer spacer columns, which makes the PSCLC film containing polymer spacer columns have a great potential to be applied in the field of flexible devices.

Optical switch with an ultralow DC drift based on thin-film lithium tantalate.

We present an electro-optic (EO) switch with ultralow DC drift on a thin-film lithium tantalate (TFLT) platform, even with SiO2 cladding and without post-annealing processes. The flat Vπ and EO responses have been measured across various driving frequencies, input optical powers, and temperatures. Stable optical switching is achievable in the low-frequency range. The experiment also demonstrated superior long-term stability (up to 2 h) compared to thin-film lithium niobate optical switches under similar on-chip optical power conditions (around -8 dBm).

Ultra-low-power consumption silicon electro-optic switch based on photonic crystal nanobeam cavity

Ultra-low-power consumption and high-speed integrated switches are highly desirable for future data centers and high-performance optical computers. In this study, we proposed an ultra-low-power consumption silicon electro-optic switch based on photonic crystal nanobeam cavities on a foundry platform. The proposed switch showed an ultra-low static-tuning power of 0.10 mW and a calculated dynamic switching power of 6.34 fJ/bit, with a compact footprint of 18 μm × 200 μm. Additionally, a 136-Gb/s four-level pulse amplitude modulation signal transmission experiment was carried out to verify the capability of the proposed electro-optic switch to support high-speed data transmission. The proposed device has the lowest static-tuning power consumption among silicon electro-optic switches and the highest data transmission rate. The results demonstrate the potential applications of this switch in high-performance optical computers, data center interconnects, optical neural networks, and programmable photonic circuits.

The electrical properties of nitrogen-doped vanadium dioxide thin films grown by magnetron sputtering

Abstract Vanadium dioxide (VO2) undergoes a reversible semiconductor-metal phase transition near 68°C, and the optical and electrical properties could be changed in femtoseconds. These unique characteristics meet the electro-optic switch applications. In this work, to improve the intrinsic characteristics of VO2, a series of nitrogen-doped vanadium dioxide thin films were prepared by reactive magnetron sputtering. Moreover, the effects of different nitrogen flow rates on the microstructure, surface morphology, electrical properties and phase transition properties of the samples were investigated. The samples are characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), four-point probe system, and Hall effect et al. Sheet resistance variation at room temperature and high temperatures indicates remarkable semiconductor-metal transition characteristics. According to results of Hall effect measurement, when nitrogen flow rate is less than 1 sccm, the samples exhibits p-type semiconductor characteristics. However, while nitrogen flow rate reaches 1 sccm, n-type semiconductor characteristics appear. What’s more, Carrier mobility reaches a maximum at a nitrogen to oxygen flow ratio of 0.3. The results reveal that the samples have a great potential on electro-optic switching applications.

Phase-Controlled Synthesis and Phase-Change Properties of Colloidal Cu-Ge-Te Nanoparticles.

Phase-change memory (PCM) technology has recently attracted a vivid interest for neuromorphic applications, in-memory computing, and photonic integration due to the tunable refractive index and electrical conductivity between the amorphous and crystalline material states. Despite this, it is increasingly challenging to scale down the device dimensions of conventionally sputtered PCM memory arrays, restricting the implementation of PCM technology in mass applications such as consumer electronics. Here, we report the synthesis and structural study of sub-10 nm Cu-Ge-Te (CGT) nanoparticles as suitable candidates for low-cost and ultrasmall PCM devices. We show that our synthesis approach can accurately control the structure of the CGT colloids, such as composition-tuned CGT amorphous nanoparticles as well as crystalline CGT nanoparticles with trigonal α-GeTe and tetragonal Cu2GeTe3 phases. In situ characterization techniques such as high-temperature X-ray diffraction and X-ray absorption spectroscopy reveal that Cu doping in GeTe improves the thermal properties and amorphous phase stability of the nanoparticles, in addition to nanoscale effects, which enhance the nonvolatility characteristics of CGT nanoparticles even further. Moreover, we demonstrate the thin-film fabrication of CGT nanoparticles and characterize their optical properties with spectroscopic ellipsometry measurements. We reveal that CGT nanoparticle thin films exhibit a negative reflectivity change and have good reflectivity contrast in the near-IR spectrum. Our work promotes the possibility to use PCM in nanoparticle form for applications such as electro-optical switching devices, metalenses, reflectivity displays, and phase-change IR devices.

Enhanced electro-chemical characteristics and superior electro-optical switching performance of nematic liquid crystal doped with MgO nanoparticles

Enhanced electro-chemical characteristics and superior electro-optical switching performance of nematic liquid crystal doped with MgO nanoparticles

High-performance electro-optic switches with compact multimode interference and Bezier S-bend waveguides

High-speed and energy-efficient electro-optic (EO) switches are crucial for next-generation data communication systems. This paper presents a novel EO switch utilizing a multimode interference (MMI) coupler-based approach on a lithium-niobate (LiNbO3) platform. The switch is designed with Bezier S-bend waveguides, leading to a significant reduction in bending loss to 0.18 dB. This Bezier-bend EO switch shows an excess loss of 0.33 dB and crosstalk of −20.44 dB for the bar port switching, while the cross port switching exhibits an excess loss of 0.64 dB and crosstalk of −13.66 dB. Applying a 3.27 V voltage achieves a balanced splitting ratio of 29:29:29 between the three outputs. The length of this EO switch is 4.09 mm, which requires 4.1 V to create a phase shift, showing a voltage efficiency of 1.68 V.cm. This paper presents a promising pathway for a novel EO switch design and introduces improved signal management for next-generation computing systems.

Effects of Composition and Polymerization Conditions on the Electro-Optic Performance of Liquid Crystal-Polymer Composites Doped with Ferroelectric Nanoparticles.

The presence of a polymer network and/or the addition of ferroelectric nanoparticles to a nematic liquid crystal are found to lower transition temperatures and birefringence, which indicates reduced orientational order. In addition, the electro-optic switching voltage is considerably increased when a polymer network is formed by in situ polymerization in the nematic state. However, the resulting polymer network liquid crystal switches at similar voltages as the neat liquid crystal when polymerization is performed at an elevated temperature in the isotropic state. When nanoparticle dispersions are polymerized at an applied DC voltage, the transition temperatures and switching voltages are reduced, yet they are larger than those observed for polymer network liquid crystals without nanoparticles polymerized in the isotropic phase.

Optical properties of Ba-impurity defect clusters in KH2PO4 crystals

Potassium dihydrogen phosphate (KDP) is widely used in electro-optical switches and inverter crystals in inertial confinement fusion (ICF). The early studies suggested that defect clusters are one of the main reasons why the laser-induced damage threshold (LIDT) is far lower than the theoretical value. However, it is not clear what type of defect clusters cause this phenomenon. The BaK defect cluster models have been determined by simulation using General Utility Lattice Programs (GULP). We found that BaK+VH and BaK+VK cause a dramatic distortion on H-O bonds with maximum values of 29.5 % and 27.12 %, respectively. By analyzing the configuration coordinate diagram and optical spectra, we believe that both defect clusters can promote ionization through defect-assisted "2+1" photon absorption, which leads to free electrons more easily exceeding the critical value for electron avalanche breakdown. Our study will offer insight into the effects of defect clusters in KDP crystals.

Enhanced dielectric properties and electro-optic switching responses of Ag–In–S quantum dots-doped nematic liquid crystal

Enhanced dielectric properties and electro-optic switching responses of Ag–In–S quantum dots-doped nematic liquid crystal

Stepwise Progression of Dye-Induced In Situ Photoalignment and Subsequent Stabilization for Noncontact Alignment of Liquid Crystals.

Noncontact alignment of liquid crystals (LCs) is crucial for large-area and ultrahigh definition (UHD) display manufacturing. This research presents an innovative approach to the photoalignment of LCs, aiming to overcome challenges associated with uniformity and assembly in large-sized and UHD displays. Using homogeneously dissolved, nonionic azobenzene chromophores sensitive to both visible and UV light, we demonstrate an in situ stepwise progression of dye-induced LC alignment and subsequent stabilization using reactive mesogen (RM). Both dual-wavelength and single-wavelength approaches enable stepwise interfacial modifications for LC alignment and stabilization. The dye-induced LC alignment is rewritable, allowing for the creation of various patterns and gray-level alignments. The stability of the alignment is ensured through cross-linked RM layers, providing a robust and permanent solution for LC alignment without the need for delicate mechanical treatments. Importantly, this method addresses the challenges associated with conventional photoalignments, including various dye-induced approaches and high-energy photoalignment. The proposed method exhibits high-quality electro-optical switching, azimuthal anchoring strength, and stability against thermal, radiation, and ac-field stresses, making it a promising candidate for commercial mass production, especially in the fabrication of large-sized and UHD LC displays.

Compact non-volatile multilevel Sb2Se3 electro-optical switching in the mid-infrared group-IV-photonics platform

This theoretical modeling and simulation paper presents designs and projected performances of two non-volatile, broadband, on-chip 2 × 2 electro-optical switches based upon the germanium-on-insulator (GeOI) photonic-electronic platform operating at the 2.5 µm mid-infrared wavelength. These compact devices facilitate large-scale integration on a “monolithic wafer” where all components are made of group-IV semiconductors. The switches are the two-waveguide directional coupler (DC) and the Mach-Zehnder interferometer (MZI). A thin-film graphene Joule-effect micro-heater is assumed on the planarized GeOI device to change the phase (reversably) of DC-slot-embedded Sb2Se3 phase-change material (PCM) from crystalline to amorphous. The MZI has this PCM within its slotted-arm waveguides. Simulations show high-performance bistable or multi-stable cross-bar switching in both devices. The 2 × 2 DC has an active coupling length of 17 µm, 130 nm gap, and a footprint of 5 µm x 31 µm. The device bandwidth is 30 nm over a wavelength range where cross and bar insertion losses IL are less than 0.3 dB, and where optical crosstalk is less than −15 dB. Results for the 2 × 2 MZI show crossbar switching attained with a 7.8 µm-length Sb2Se3 slot and a 5 µm x 51 µm switch footprint. Stable, multi-level switching in both devices is attained via partial amorphization. Thermal modeling shows that careful control of the voltage-pulse amplitude V applied to graphene (rectangular pulse duration of 500 ns) can give 32 levels, for example, using V in the range from 6.18 to 7.75 Volts. Multi-level switching is shown also in PCM-based ring resonators.

Ferroelectric Smectic Liquid Crystals

Since the discovery of the first ferroelectric liquid crystal (FLC) in the chiral smectic C (SmC*) phase, ferroelectricity in liquid crystals has attracted much attention due to not only the fundamental interest but also the applications. This review focuses on the evolution of the design concept for ferroelectric smectic liquid crystals. It progresses from considering macroscopic phase symmetry to designing intermolecular interactions. For the purpose of understanding the molecular organization in smectic phases, we propose a dynamic model of constituent molecules in the smectic A (SmA) and SmC* phases based on 13C NMR studies. Then, we follow the structure–property relationship in ferroelectric SmC* liquid crystals for FLC displays. We reconsider de Vries-like materials that can provide defect-free alignment. We pay attention to the electro-optical switching in the chiral de Vries smectic A phase. Finally, we show several liquid crystals exhibiting polar smectic A phases and discuss how the polar order occurs in the highest symmetric smectic A phase.

A novel double-layer liquid crystal electro-optic switch and its infrared shielding properties investigation

ABSTRACT In this study, a novel light switch was developed by integrating polymer dispersion liquid crystals (PDLC) and polymer-stabilised cholesteric liquid crystals (PSCLC), leveraging the infrared shielding properties of these two liquid crystal films. The optimal formulation for each layer of the liquid crystal structure was investigated. Subsequently, the effects of light intensity, high temperature, and humidity on the performance of the light switch were examined. This new light switch can be selectively driven layer by layer at room temperature, achieving three states: the off state, PDLC layer-driven state, and full-driven (on state). This functionality serves the purpose of electrogenerated temperature control. Samples under optimal conditions exhibited a 31% enhancement in infrared shielding compared to a single-layer PDLC film. Moreover, the IR shielding rate could be adjusted according to the voltage applied, realising an intelligent temperature-control effect. The results of this study suggest that such bilayer liquid crystal structures hold significant potential for application in electro-optical devices and smart curtain systems.

Collective molecular relaxations and electro-optical switching response of a wide room temperature antiferroelectric liquid crystal mixture

Antiferroelectric liquid crystals (AFLCs) are advanced smart materials for displays with unique properties of tristate switching. Thermodynamic, dielectric and switching characteristics of a room temperature bicomponent AFLC mixture at eutectic composition was investigated in the present work. The emergence of various phases in the eutectic composition was identified on the basis of observed dielectric relaxation modes and other parameters. Critical electric field (Ec) to unwind the helix, spontaneous polarization (Ps), torsional viscosity (γt) and switching time (ts) have been determined in the ferroelectric (SmC*) and the antiferroelectric (SmCA*) phases from switching experiments. Spontaneous polarization follows the equation, Ps = Po(1-T/Tc)γ in the temperature range of tilted chiral smectic phases, with values of Tc = 91.8 ± 0.1 °C and γ = 0.410 ± 0.005. Value of γ indicates that the SmA* to SmC* transition is of the first order as observed by the enthalpy measurements from the thermodynamic studies. In the AFLC phase of interest, ts is ∼2–3 ms and Ps∼200 nC/cm2. These parameters suggest that the mixture is appropriate base material for electro-optical applications.

Double plasmon-induced transparency 3 bit graphene encoder

In this paper, a 3 bit encoder was proposed which was based on double plasmon-induced transparency (PIT) effect. This structure consists of the bright-bright mode and realizes a double PIT window in the 0.1–3 THz range. Electric field distributions reveal that the double PIT effect is originated from the strong destructive interference between three bright modes, the Lorentz oscillation coupling model is utilized to confirm the finite-integration time-domain (FITD) simulation regardless of the x-polarization direction or y-polarization direction. When the incident light is x-polarized, encoding frequencies were at 0.976 THz, 1.525 THz and 2.069 THz, respectively; while in y-polarization, encoding frequencies were at 1.579 THz, 1.935 THz and 2.589 THz, respectively. Results depict that the Modulation Depth (MD) could reach 98 % regardless of the x-polarization direction or the y-polarization direction. As an electro-optical switch, the maximum MD could reach ≥98 %, the minimum IL could reach 0.35 dB, the maximum ER could reach ≥14 dB. Besides the encoder, the proposed structure is of great importance for the design of optical switches, terahertz modulators and slow light devices.

Design and Simulation of a silicon electro-optic microring switch with a graphene modulating layer

This paper presents a comprehensive simulation study on the design and simulation of an electro-optic ring switch utilizing graphene material. The switch employs the electrically Tunable Refractive Index by graphene to modulate the transmission characteristics within a ring resonator structure. By applying an electrical voltage ranging from -6 to -10V, significant changes are noticed in the output ports' transmission characteristics. In particular, the transmission through the output ports varies between 81% to 18% for output port n.1 and 21% to 83%for output port no.2, proving that signal propagation can be effectively controlled and manipulated. In addition to demonstrating the electro-absorption capabilities of graphene, this study explores the complex mechanics involved in the switching process. The relationship between the applied voltage and the optical characteristics of graphene is clarified by thorough simulations, providing insight into the switch's dynamic behavior. Furthermore, the efficiency, response time, and Electrical bandwidth of the device are discussed, offering a glimpse into its possible use in photonic integrated circuits and telecommunications. Overall, this study not only unveils the promising prospects of graphene-based electro-optic ring switches but also contributes to advancing the understanding of novel materials for next-generation photonic devices.

Exploring Quantum Dots Size Impact at Phase Diagram and Electrooptical Properties in 8CB Liquid Crystal Soft-Nanocomposites.

We explore the influence of functionalized core-shell CdSe/ZnS quantum dots on the properties of the host liquid crystal compound 4-cyano-4'-octylbiphenyl (8CB) through electrooptical measurements. Two different diameters of quantum dots are used to investigate the size effects. We assess both the dispersion quality of the nanoparticles within the mixtures and the phase stability of the resulting anisotropic soft nanocomposites using polarizing optical microscopy. The temperature-mass fraction phase diagrams of the nanocomposites reveal deviations from the linear behavior in the phase stability lines. We measure the birefringence, the threshold voltage of the Fréedericksz transition, and the electrooptic switching times of the nanocomposite systems in planar cell geometry as functions of temperature, mass fraction, and diameter of the quantum dots. Beyond a critical mass fraction of the dopant nanoparticles, the nematic order is strongly reduced. Furthermore, we investigate the impact of the nanoparticle size and mass fraction on the viscoelastic coefficient. The anchoring energy at the interfaces of the liquid crystal with the cell and the quantum dots is estimated.