Electro-optic Switch Research Articles

Low threshold electro-optic switch and TE/TM polarization selector using liquid crystal channel waveguide

We demonstrate a Liquid Crystal (LC) core channel waveguide-based low threshold electro-optic switch by employing in-plane switching configuration and show its application for polarization selection device. The waveguide is fabricated on an indium tin oxide (ITO) coated glass substrate using the laser direct writing lithography technique. We have experimentally shown that the Freedericksz transition voltage of LC molecules is ∼ 1 V, and it relatively requires a low threshold voltage of ∼ 2 V to switch on the waveguide. The measured extinction ratio of the device is greater than 18 dB, along with a low insertion loss of ∼ 3.27 dB as compared to the conventional LC waveguides. The fabricated device is further demonstrated as a voltage-controlled polarization selector that passes either TM or TE-polarized light with a polarization extinction ratio of 28 dB and 25 dB, respectively. The proposed device exhibits the features such as low voltage control, low optical and insertion loss, high extinction ratio, and an externally controlled polarization selector, which are the key requirements in integrated photonics.

A silicene-based plasmonic electro-optical switch in THz range

The first design and simulation of a silicene-based optical switch in the frequency range of 20 to 50 THz are presented. Silicene is a monolayer of silicon atoms stacked together in the shape of a honeycomb that has outstanding features such as compatibility with current technology, strong spin-orbital coupling, and attractive optical properties. The proposed switch consists of a silicene waveguide encapsulated between layers of which transmits the input signal by emitting surface plasmon polaritons. To control the ON and OFF switching modes using impurities and DC voltage, we change the chemical potential of silicene. The main advantages of the proposed switch over similar graphene types are fewer losses, broadband frequency range, more compatibility with current technology, and also due to the encapsulation of silicene between the waveguide is isolated from the environment. Also, Q-factor, insertion loss, and extinction ratio for the proposed switch are 189, 0.39 dB, and 51 dB, respectively.

Design of Monolithic 2D Optical Phased Arrays Heterogeneously Integrated with On-Chip Laser Arrays Based on SOI Photonic Platform.

In this work, heterogeneous integration of both two-dimensional (2D) optical phased arrays (OPAs) and on-chip laser arrays based on a silicon photonic platform is proposed. The tunable multi-quantum-well (MQW) laser arrays, active switching/shifting arrays, and grating antenna arrays are used in the OPA module to realize 2D spatial beam scanning. The 2D OPA chip is composed of four main parts: (1) tunable MQW laser array emitting light signals in the range of 1480-1600 nm wavelengths; (2) electro-optic (EO) switch array for selecting the desired signal light from the on-chip laser array; (3) EO phase-shifter array for holding a fixed phase difference for the uniform amplitude of specific optical signal; and (4) Bragg waveguide grating antenna array for controlling beamforming. By optimizing the overall performances of the 2D OPA chip, a large steering range of 88.4° × 18° is realized by tuning both the phase and the wavelength for each antenna. In contrast to the traditional thermo-optic LIDAR chip with an external light source, the overall footprint of the 2D OPA chip can be limited to 8 mm × 3 mm, and the modulation rate can be 2.5 ps. The ultra-compact 2D OPA assembling with on-chip tunable laser arrays using hybrid integration could result in the application of a high-density, high-speed, and high-precision lidar system in the future.

Deterministic topological defects and quantum dot assembly in a nematic liquid crystalline medium

Liquid crystal (LC) materials exhibit interesting electro-optic switching and molecular ordering properties. Furthermore, the addition of chemically compatible active emitters such as core-shell quantum dots (QD) in a LC medium allows optical as well as dielectric tuning in an anisotropic, reconfigurable ordered medium. Order in a nematic LC phase is characterized by an orientational order parameter. In this work, we demonstrate the use of patterned substrates to generate arrays of integer topological defects in a nematic LC medium doped with cadmium selenide (core) cadmium sulfide (shell) core–shell QDs. We demonstrate the formation of metastable air-pillar-induced integer topological defects (TDs) in relatively thinner 9 μm LC sandwich cells, and the formation of field-induced TDs in thicker (25 μm) cells. Simultaneously, the self-assembly of core-shell QDs into square arrays on the patterned substrates is discussed, highlighting potential electro-optic device applications. The surfactant hexadecyltrimethylammonium bromide (CTAB) is found to play a significant role in LC TD formation as well as QD spatial organization at the optimized concentration. Self-assembly and ordering of single- and multi-component LCs within structured devices is a highly relevant problem for modern optoelectronic devices. This work opens new possibilities for classical as well as quantum light sources which require spatially ordered optical emitters in a reconfigurable dielectric medium at a micron-scale.

Simultaneous electro-optic spectral switching and Q switching in a dual-wavelength Nd:YVO4 laser based on an aperiodic optical superlattice lithium niobate.

We report the demonstration of an electro-optic (EO) switchable dual-wavelength (1064- and 1342-nm) Nd:YVO4 laser based on an aperiodically poled lithium niobate (APPLN) chip whose domain structure is designed using aperiodic optical superlattice (AOS) technology. The APPLN works as a wavelength-dependent EO polarization-state controller in the polarization-dependent laser gain system to enable switching among multiple laser spectra simply by voltage control. When the APPLN device is driven by a voltage-pulse train modulating between a VHQ (in which target laser lines obtain gain) and a VLQ (in which laser lines are gain suppressed), the unique laser system can produce Q-switched laser pulses at dual wavelengths 1064 and 1342 nm, single wavelength 1064 nm, and single wavelength 1342 nm, as well as their non-phase-matched sum-frequency and second-harmonic generations at VHQ = 0, 267, and 895 V, respectively. A laser can benefit from such a novel, to the best of our knowledge, simultaneous EO spectral switching and Q switching mechanisms to increase its processing speed and multiplexity for versatile applications.

Optical and laser damage properties of 98% deuterium DKDP crystal in different crystal orientations

Served as electro-optic switch, frequency converter and the optical parametric chirped pulse amplifier (OPCPA), highly deuterated DKDP crystals are critical optical elements in high power laser systems. In our work, samples taken in Z direction and Ⅰ-type phase-match direction from an as-grown high deuterium DKDP crystal, which was grown by the rapid growth method with continuous filtration. Thermo-gravimetric apparatus (TGA) measurement was applied to obtain the deuterium content of the DKDP crystal. the results showed the deuterium level of the samples in our experiments exceeded 98%. The ultraviolet–visible–near-infrared transmittance spectrum showed that the transmittance of Z-cut at 532 nm and Ⅰ-type at 1064 nm were 92.99% and 96.07%, respectively. The 0% laser-induced damage threshold of Z-cut in 1064 nm was about 40J/cm2, exceeding much more than the application requirement in certain high power laser systems. The polarization state of laser had little effect on the laser-induced damage characteristics of Ⅰ-type sample. Then the laser-induced damage morphologies of 98% DKDP crystals induced by the 1064 nm and 532 nm lasers were investigated. The results indicated that the "micro-explosion" of different kinds of defects in the bulk led to different damage morphologies, and many cracks in the damage pinpoints presented the regular orientation with better consistency in view of the Ⅰ-type phase-match direction. Our research can provide a reference for the applications of highly deuterated DKDP crystals in high power laser systems.

Feasibility of chipscale integration of single-photon switched digital loop buffer

A strategy for realizing a microchip-scale single-photon digital loop buffer controlled by low-voltage electronic signals is studied in the context of integrated photonics. A potential implementation for bridging a gap between other technologies uses a recirculating loop architecture based on advances in low-loss passive waveguides and a fast electro-optic add-drop switch. Though the requirements of single-photon buffers are demanding, our analysis suggests that a voltage-controlled, room-temperature catch-and-store short-term quantum memory for light on a chip may be feasible in certain regimes.

Ultracompact topological photonic switch based on valley-vortex-enhanced high-efficiency phase shift

Topologically protected edge states based on valley photonic crystals (VPCs) have been widely studied, from theoretical verification to technical applications. However, research on integrated tuneable topological devices is still lacking. Here, we study the phase-shifting theory of topological edge modes based on a VPC structure. Benefiting from the phase vortex formed by the VPC structure, the optical path of the topological edge mode in the propagation direction is approximately two-fold that of the conventional optical mode in a strip waveguide. In experiments, we show a 1.57-fold improvement in π-phase tuning efficiency. By leveraging the high-efficiency phase-shifting properties and the sharp-turn features of the topological waveguide, we demonstrate an ultracompact 1 × 2 thermo-optic topological switch (TOTS) operating at telecommunication wavelengths. A switching power of 18.2 mW is needed with an ultracompact device footprint of 25.66 × 28.3 μm in the wavelength range of 1530–1582 nm. To the best of our knowledge, this topological photonic switch is the smallest switch of any dielectric or semiconductor 1 × 2/2 × 2 broadband optical switches, including thermo-optic and electro-optic switches. In addition, a high-speed transmission experiment employing the proposed TOTS is carried out to demonstrate the robust transmission of high-speed data. Our work reveals the phase-shifting mechanism of valley edge modes, which may enable diverse topological functional devices in many fields, such as optical communications, nanophotonics, and quantum information processing.

Proposal of an infrared electro-optic switch based on grapheme–silicone–graphene metamaterial with electrically dynamic tunability

Proposal of an infrared electro-optic switch based on grapheme–silicone–graphene metamaterial with electrically dynamic tunability

Extremely High Kerr Constant and Low Operating Voltage in a Stable Room-Temperature Blue Phase III Derived from Three-Ring-Based Bent-Core Molecules.

In this study, we used a new series of highly polar three-ring-based bent-core liquid crystals (BCLCs) to stabilize a wide temperature range of blue phase III (BPIII), including room temperature. A significant finding is the implementation of electro-optical (E-O) switching at room temperature in the current BPIII system. The observed Kerr constant (K) has an extraordinarily high value (K ≈ 9.2 × 10-9m V-2) that exceeds all previously reported values in the category of BPIII materials. The extremely high value of K realizes the lowest operating voltage (Von ≈ 3.3 Vrms/μm) for BPIII. The measured values of K and Von in BPIII set a new limit for the experimentalist. The millisecond (ms) order response times are explained based on rotational viscosity. The present binary system of BPIII materials is an excellent choice for device application.

Double Narrowband Induced Perfect Absorption Photonic Sensor Based on Graphene–Dielectric–Gold Hybrid Metamaterial

Double narrowband induced perfect absorption in the terahertz region is achieved in a graphene–dielectric–gold hybrid metamaterial, whose physical mechanism is analyzed using the coupled-mode theory (CMT), which agreed well with the finite-difference time-domain (FDTD) simulation. This study found that the Fermi level of graphene can be adjusted to improve the absorptivity when the refractive index (RI) nd of the chosen dielectric cannot achieve a good absorption effect. In addition, the blue shift of absorption spectrum can be used in the design of dual-frequency electro-optical switches, of which the modulation degree of amplitude (MDA) can reach as high as 94.05% and 93.41%, indicating that this is a very promising electro-optical switch. Most significantly, the RI sensing performance is investigated, which shows an ultra-high absorption sensitivity SA = 4.4°/RIU, wavelength sensitivity Sλ = 9.8°/RIU, and phase shift sensitivity Sφ = 2691°/RIU. At last, an interesting finding is that the two peaks (R1 and R2) of plasmon-induced absorption (PIA) show different polarization characteristics (insensitive or sensitive) to the incident light angle; this polarization-sensitive is particularly important for the PIT/PIA-based optical polarizers. Undoubtedly, this paper is of great significance to the research and design of terahertz photonic devices and sensors.

Dynamically Tunable and Multifunctional Polarization Beam Splitters Based on Graphene Metasurfaces.

Based on coupled-mode theory (CMT) and the finite-difference time-domain (FDTD) approach, we propose a graphene metasurface-based and multifunctional polarization beam splitter that is dynamically tunable. The structure, comprising two graphene strips at the top and bottom and four triangular graphene blocks in the center layer, can achieve triple plasma-induced transparency (PIT). In a single polarization state, the computational results reveal that synchronous or asynchronous six-mode electro-optical switching modulation may be performed by modifying the Fermi levels of graphene, with a maximum modulation degree of amplitude (MDA) of 97.6% at 5.148 THz. In addition, by varying the polarization angle, a polarization-sensitive, tunable polarization beam splitter (PBS) with an extinction ratio and insertion loss of 19.6 dB and 0.35 dB at 6.143 THz, respectively, and a frequency modulation degree of 25.2% was realized. Combining PIT with polarization sensitivity provides a viable platform and concept for developing graphene metasurface-based multifunctional and tunable polarization devices.

МЕТОДИ ПІДВИЩЕННЯ ЗАВАДОСТІЙКОСТІ ВИСОКОТОЧНИХ ЛАЗЕРНИХ ОПТОЕЛЕКТРОННИХ СИСТЕМ ДЛЯ ВИМІРЮВАННЯ ЛІНІЙНИХ ПЕРЕМІЩЕНЬ

It is shown that in high-precision optoelectronic systems for measuring the linear displacements of objects with diffuse-reflecting surface, built on the basis of phase laser rangefinders, to ensure a given accuracy, it is necessary to compensate for the effect on the measurement of harmonic noise. Methods of compensation of this influence which are based on use of various algorithms of measurement of a phase shift proportional to distance which is defined are considered and analyzed. The disadvantages and advantages of each of the methods are evaluated, recommendations for their use are made. It is proposed to compensate for the harmonic interference of the use of electro-optical switches. References 12, figures 3.

Scalable 3D Silicon Optical Switch Based on CLOS Architecture

To achieve complex functionality with small size, weight and power, photonic integrated circuits (PIC) are expanded from two-dimensional (2D) to three-dimensional (3D). In this paper, a new design for a scalable 3D silicon optical switch is proposed. Key elements, including silicon electro-optic switches, crossings, and interlayer transitions are used to define and optimize the 3D optical switching network. The architecture is based on CLOS architecture, which can be extended to multiple layers. Silicon-based two- and three-layer switches are carefully designed and analyzed as an example based on the transfer matrix technique (TMT). In a 4×4 two-layer optical switch, the average insertion loss at 1550 nm wavelength is ∼4.16 dB, and ∼3.69 dB for the “all-cross” and “all-bar” states, respectively. In a 4×4 three-layer optical switch, the average insertion loss at 1550 nm wavelength is ∼5.96 dB, and ∼5.41 dB for the “all-cross” and “all-bar” states, respectively. The architecture also shows the scalability of both the port number and the layer number. The scalable 3D architecture proposed could improve the interconnect density twice and thrice in a single-layer design.

Pseudopeptidic polymers for modulating electro-optic switching, dielectric and electrical properties of liquid crystal

Herein, we report the stabilization of a nematic liquid crystal using chiral amino acid-based polymers. For the first time, the effect of molecular weight of structurally similar polymers on the physical parameters of polymer-stabilized liquid crystals (PSLCs) is investigated. To obtain PSLCs, three pseudopeptidic bottlebrush polymers of different molecular weights are synthesized from the same monomer using a ring-opening metathesis polymerization (ROMP) reaction. The bottlebrush polymers form self-assembly networks in the LC matrix. The size of the self-assembled network is readily tunable by the systematic variation in the molecular weight of the constituent polymer. The polymer network assembly is characterized by using field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and polarizing optical microscopy (POM). The ion density and diffusion coefficient of two different types of mobile ions are calculated by utilizing experimental dielectric data. The constituent polymer determines the structure of self-assembly network in PSLC and hence, the dielectric, electrical, electro-optic, and optical properties. The PSLCs show significant improvement in the response time (∼21%), dielectric anisotropy (∼40%), conductivity (∼11%), current (5-fold increment at 20 V), and phase transition temperature (PTT) upon variation in the molecular weight of the doped polymer units. This simple method of tuning response time, dielectric anisotropy, conductivity, current, and PTT using polymers of different molecular weights presents several possibilities of fabricating optoelectronic devices.

Improvement of Overlap for 2x2 MZI Electro-Optic Switch Based on Lithium Tantalite (LiTaO3)

This research introduces a method of an electro-optic effect and electro-refractive effect that considers very imperative for high-speed optical communication systems. In this research, it presents way by a reduction the gap between the electrodes d, and this technique achieves to solve the problem of overlap for Mach-Zehnder interferometer MZI electro-optical switch base on lithium tantalite LiTaO3, also this technique suggests a model for analysis the effect parameters on the electro-optic overlap of the electro-optic switch as the ordinary positive changing of refractive index and a length of arm switch. This study achieves a better overlap by large positive changing refractive index with a suitable small length of arm about 8µm and low driving power at least 4V/µm. Also, for lithium tantalite LiTaO3, this research achieves a better performance for system using the near infrared wavelength.

Electrical modification of order parameters and director fluctuations in a dielectrically negative nematic doped with a positive additive

Electric effects of nematic liquid crystals (NLCs) have enabled the revolution of the display industry. Recently, the electro-optic switching of NLCs has been accelerated by applying electric fields in such a way that the field does not change the director orientation, but modifies the optical tensors of NLCs due to three effects: induced biaxial orientational order, enhanced uniaxial orientational order, and quenching of director fluctuations. Till now, these three effects have been explored only in NLCs with negative dielectric anisotropy. Here, we experimentally study the electrical modification of order parameters and director fluctuations in a dielectrically negative/positive composite NLC. The dielectrically positive dopant causes the following changes: (a) a faster nanosecond switching for optical responses attributed to the change of order parameters, (b) an increase of the biaxial order parameter, (c) a reduction of the uniaxial order parameter, and (d) a slight reduction in the field-induced birefringence change. This work provides a basis for further studies in nanosecond electro-optics.

Analysis of interferometric configuration for optical devices

Abstract With the exponential growth in information related applications and the continuous increase in voice over IP (VoIP) applications, the carriers are expanding their networks to provide improved services to their end users. In such cases, the synchronous optical network/synchronous digital hierarchy model is not suitable. In this work, we are going to investigate the electro optic switch with the help of a VB script to simulate the device for various parameters. Further, we will then scan the central electrode voltages and take account of the overlap integral taking place at the output port with the help of waveguide mode. The best switching for switches at different voltages so as to have negligible coupling loss for different input signals is investigated. We aim to evaluate the MZI switches with the Li-Tn channel profile wave guiding structure and confirm their performance as compared to the existing MZI switches.

Broadband tunable electro-optic switch/power divider as potential building blocks in integrated lithium niobate photonics.

We demonstrate an electro-optic (EO) switch or in general, an EO controllable power divider based on a periodically poled lithium niobate (PPLN) polarization mode converter (PMC) and a five-waveguide adiabatic coupler integrated on a Ti:LN photonic circuit chip. In this integrated photonic circuit (IPC) device, the PPLN works as an EO controllable polarization rotator (and therefore a PMC), while the adiabatic coupler functions as a broadband polarization beam splitter (PBS). The 1-cm long PPLN EO PMC of the IPC device is characterized to have a half-wave (or switching) voltage of Vπ∼20 V and a conversion bandwidth of ∼2.6 nm. The splitting ratios of the adiabatic coupler PBS in the IPC device are >99% for both polarization modes over a broad spectral range from 1500-1640 nm. The EO mode of the implemented IPC device is activated when the PPLN EO PMC section is driven by an external voltage; the characterized EO switching/power division behavior of the device is in good agreement with the theoretical fit. The tunability of the EO IPC device in the 100-nm experimental spectral range is also demonstrated via the temperature tuning. The featured broad tunability and high integrability of the EO device presented in this study facilitates it to be an advantageous building block for realizing an on-chip photonic system.

Multiple ferroelectric nematic phases of a highly polar liquid crystal compound

ABSTRACT Ferroelectric nematic liquid crystals represent not only fascinating, fundamental science, but they also hold promise for new technologies including high-density power storage or sub-millisecond switching information displays. In this work, we describe the synthesis and measurements of the physical properties of a new compound, 4-nitrophenyl 4-[(2,4-dimethoxylbenzoyl)oxy]-2-fluorobenzoate (RT11001). This material exhibits multiple, highly polar, ferroelectric nematic phases that have not been previously reported. We employ a wide range of physical characterisation methods including differential scanning calorimetry (DSC), mass density measurement, optical birefringence, polarising optical microscopy (POM), dielectric spectroscopy, electric current analysis, electro-optical switching, small-angle and wide-angle x-ray scattering measurements to show that RT11001 has multiple, distinct ferroelectric phases. We argue that the highest temperature phase is a polar nematic fluid with non-polar smectic clusters. Directly below appears to be a transition to another polar nematic phase containing polar positionally ordered clusters. Lastly, there are indications of an additional, polar biaxial liquid crystal phase at lower temperatures.