Tunable Switch Research Articles

Tunable Switching between Slow and Fast Light in the Graphene Nanodisks (GND)–Quantum Dot (QD) Plasmonic Hybrid Systems

Plasmonic nanocomposites demonstrate unique properties due to the plasmonic effects, especially those with graphene within their structures, thereby paving the way to various promising applications. In this paper, we investigate the linear properties of the graphene-nanodisks--quantum-dots hybrid plasmonic systems in the near-infrared region of the electromagnetic spectrum by numerically solving the linear susceptibility of the weak probe field at a steady state. Utilising the density matrix method under the weak probe field approximation, we derive the equations of motion for the density matrix elements using the dipole--dipole-interaction Hamiltonian under the rotating wave approximation, where the quantum dot is modelled as a three-level atomic system of Λ configuration interacting with two externally applied fields, a probe field, and a robust control field. We find that the linear response of our hybrid plasmonic system exhibits an electromagnetically induced transparency window and switching between absorption and amplification without population inversion in the vicinity of the resonance, which can be controlled by adjusting the parameters of the external fields and the system's setup. The probe field and the distance-adjustable major axis of the system must be aligned with the direction of the resonance energy of the hybrid system. Moreover, our plasmonic hybrid system offers tunable switching between slow and fast light near the resonance. Therefore, the linear properties obtained by the hybrid plasmonic system can be employed in applications such as communication, biosensing, plasmonic sensors, signal processing, optoelectronics, and photonic devices.

Electrical thermo-optic tuning of ultrahigh-Q silica microsphere with laser-induced graphene

We propose a scheme to achieve ultrahigh-quality (Q) silica microsphere electrical thermo-optic fully tunable tuning, which can keep its Q factor of around 108 during the tuning process. In this work, the rod of the silica microsphere is fixed on laser-induced graphene (LIG). The large amount of Joule heating generated by LIG energization can be effectively transferred to the microsphere, thus can achieve a wide range of electrical thermo-optic tuning. Experiment results show that such a simple and low-cost device owns an ultrahigh-Q factor of around 108, an extensive tuning range of 3.03 nm, a sensitivity of 15.37 pm/°C. Its tunable range is 2.5 times greater than its azimuthal FSR. This practical scheme keeps ultrahigh-Q factors and achieves fully tunable tuning without introducing complex processes and additional instrumentations, which has great potential for tunable filters and optical switches.

Graphene-Metal Hybrid Metamaterial for a Tunable Broadband Terahertz Linear-Polarization Conversion Switch and Linear-to-Circular Polarization

Graphene-Metal Hybrid Metamaterial for a Tunable Broadband Terahertz Linear-Polarization Conversion Switch and Linear-to-Circular Polarization

Tunable multistate terahertz switch based on multilayered graphene metamaterial

We proposed plasmonic effect-based narrow band tunable terahertz switches consisting of multilayered graphene metamaterial. Though several terahertz optical switches based on metamaterials were previously reported, these switches had complicated fabrication processes, limited tunability, and low modulation depths. We designed and simulated ingenious four- and eight-state terahertz optical switch designs that can be functional for multimode communication or imaging using the finite-difference time-domain simulation technique. The plasmonic bright modes and transparency regions of these structures were adjusted by varying the chemical potential of patterned graphene layers via applying voltage in different layers. The structures exhibited high modulation depth and modulation degree of frequency, low insertion loss, high spectral contrast ratio, narrow bandwidth, and high polarization sensitivity. Moreover, our proposed simple fabrication process will make these structures more feasible compared to previously reported terahertz switches. The calculated modulation depths were 98.81% and 98.71%, and the maximum modulation degree of frequencies were $$\sim$$ 61% and $$\sim$$ 29.1% for four- and eight-state terahertz switches, respectively. The maximum transmittance in transparency regions between bright modes and the spectral contrast ratio were enumerated to be 95.9% and $$\sim$$ 96%, respectively. The maximum insertion losses were quite low with values of 0.22 dB and 0.33 dB for four- and eight-state terahertz switches, respectively. Our findings will be beneficial in the development of ultra-thin graphene-based multistate photonic devices for digital switching and sensing in the terahertz regime.

Strain-induced magnetic phase transition, magnetic anisotropy switching and bilayer antiferromagnetic skyrmions in van der Waals magnet CrTe2.

In recent years, considerable attention has been paid to the research of peculiar magnetism in two-dimensional (2D) van der Waals (vdW) layered materials. Here, we unveil the major features and deep physical mechanisms of a magnetic phase transition and magnetic anisotropy switching in monolayer CrTe2 and antiferromagnetic (AFM) skyrmions in bilayer CrTe2via first-principles calculations and micromagnetic simulations. We find that a magnetic phase transition from stripy-type AFM to ferromagnetic (FM) order can be induced by applying a tensile strain of 3%. More interestingly, the magnetic easy axis can be switched between in-plane and off-plane via adjusting the magnitude of strain. Besides, the topologically protected bilayer AFM skyrmion is stabilized by a large Dzyaloshinskii-Moriya interaction (DMI) of 1.43 meV and a skyrmion lattice can be induced by a magnetic field of 6.9 T at 100 K. Different from the monolayer magnetic skyrmion, the bilayer AFM skyrmion is more promising in spintronic nanodevices owing to the suppressed skyrmion Hall effect. Our findings clarify the underlying mechanisms of the strain-tunable magnetic phase transition, magnetic anisotropy switching and bilayer AFM skyrmions in vdW magnet CrTe2, and also highlight the promising applications of CrTe2 in next-generation information storage devices.

Generation of symmetry-protected bound states in the continuum in a graphene plasmonic waveguide system for optical switching.

A graphene-involved plasmonic lossy system that allows coupling between surface plasmon polaritons and waveguide modes is proposed. The physical mechanism behind the hybrid resonance modes is investigated carefully through finite element method (FEM) simulations and rigorous coupled wave theory (RCWA). We demonstrate that by introducing an incident angle to break the symmetry of the structure, the bound states in the continuum (BIC) evolve to an observable quasi-BIC with new resonance dips, and the generated signals possess a very high Q-factor. Such transformation is investigated carefully by calculating the band structure of the system and the corresponding Q-factors. The results showed that the calculated results from the band structure are consistent with the simulations. In addition, the hybrid plasmonic system allows for switching modulation due to the tunability of graphene, and the max modulation depth of nearly 100% is reached. The outstanding Q-factor and dynamic tunability of this easy-to-fabricate hybrid structure may be helpful in engineering various plasmonic devices, including tunable optical switches, absorbers, sensors, etc.

Ionic liquid gated unipolar inverters with tunable switching voltage and excellent noise margin

Solution-processable organic semiconductor-based ambient-stable and flexible-compatible ionic liquid-gated inverter with a gain >10 and noise margin ≈60% paves the way for the integration of ionic liquid-gated logic components into circuits.

Electric-controlled tunable thermal switch based on Janus monolayer MoSSe

The high-performance, wide-range tunable thermal switches play a significant role in the thermal management, high-power-density intelligent devices, energy systems, etc. However, traditional thermal switch components, such as thermal diodes, suffer from poor stability, small adjustability, low time efficiency, and difficult implementation. Herein, we propose the superior electric-controlled thermal switch (ECTS) based on Janus monolayer MoSSe. The high-effective and asymmetric regulation of the thermal conductivity driven by electric field demonstrates a wide-range adjustable thermal switch ratio, where the peak value reaches 2.09 under the electric field of 0.04 VÅ−1. The underlying mechanism is revealed by electronic structures that the interactions between electrons and phonons are renormalized due to the electric field driving charge density redistribution, which ultimately modulates the phonon anharmonicity. The high-efficiency adjustable ECTS component is expected to provide new inspiration for next-generation thermal management and information processing.

Tunable resistive switching in shales

Electrically induced resistive switching is a subject of increasing scientific interest because it is a candidate for universal non-volatile memory. We demonstrate resistive switching in a natural reservoir shale. The resistance of the rocks is repeatedly switched between the high-resistance state and low-resistance state, being controlled by the setting and measuring voltages as well as the duration of excitation. The shale can be continuously switched over 40 times under appropriate voltage pulses with a maximum on/off ratio higher than 20, as well as small energy consumption and a power density of less than 1 mW/mm2 at 40 V. This phenomenon has also been observed in tight sandstones and some other sedimentary rocks. In contrast to conventional resistive memory devices, rocks with tunable properties are promising for data storage applications because of their low cost and simplicity, as well as being easily and safely disposable. Rocks and minerals with tunable properties are promising for storage applications, which may provide the functional use of those materials.

Forming-Free Tunable Analog Switching in WOx/TaOx Heterojunction for Emulating Electronic Synapses.

In this work, the sputtered deposited WOx/TaOx switching layer has been studied for resistive random-access memory (RRAM) devices. Gradual SET and RESET behaviors with reliable device-to-device variability were obtained with DC voltage sweep cycling without an electroforming process. The memristor shows uniform switching characteristics, low switching voltages, and a high RON/ROFF ratio (~102). The transition from short-term plasticity (STP) to long-term potentiation (LTP) can be observed by increasing the pulse amplitude and number. Spike-rate-dependent plasticity (SRDP) and paired-pulse facilitation (PPF) learning processes were successfully emulated by sequential pulse trains. By reducing the pulse interval, the synaptic weight change increases due to the residual oxygen vacancy near the conductive filaments (CFs). This work explores mimicking the biological synaptic behavior and further development for next-generation neuromorphic applications.

Surface engineering of mixed conjugated/polyelectrolyte brushes – Tailoring interface structure and electrical properties

HypothesisMixed polymer brushes (MPBs) could be synthesized by surface dilution of homopolymer brushes and subsequent grafting of other type of chains in the formed voids. Nanophase separation and dynamics of surface-grafted chains could be tailored by modification of their molecular architecture. Mixed polyelectrolyte and conjugated chains contribute synergistically to tailor properties of the coating. ExperimentsA new synthetic strategy that allowed spatially controlled grafting of poly(sodium 4-styrenesulfonate) chains (PSSNa) in close neighborhood of poly(3-methylthienyl methacrylate) (PMTM) brushes (precursors of the conjugated chains) using surface-initiated polymerizations was developed. The final mixed conjugated/polyelectrolyte brushes were prepared by template polymerization of pendant thiophene groups in PMTM chains. Surface dynamics and nanophase separation of MPBs were studied by nanoscale resolution IR imaging, SIMS profiling and AFM mapping in selective solvents. FindingsUnconjugated MPBs were shown to undergo vertical, and horizontal nanophase separation, while the size and shape of the nanodomains were dependent on molar ratio of the mixed chains and their relative lengths. Generation of the conjugated chains led to diminishing of nanophase separation thanks to stronger mutual interactions of conjugated PMTM and PSSNa (macromolecular mixing). The obtained systems demonstrated tunable interfacial structure and resistance switching phenomenon desired in construction of smart surfaces or memristive devices.

Probe absorption characteristics and a tunable susceptibility switch of a superconducting flux qubit coupled to two mechanical resonators

A scheme is proposed for exploring the absorption spectrum and the susceptibility of a loop-coupled hybrid system in which two mechanical resonators are coupled to a superconducting flux qubit. Theoretical analysis has shown that the transparency based on mechanically induced coherent population oscillation (MICPO) can be tuned by the Rabi frequency and the decay rate of the mechanical resonator. We put forward a new and precise scheme to measure the frequency of the mechanical resonator. Moreover, a method to design the nonlinear susceptibility switches is also provided. Simultaneously, the coupling strength between two mechanical resonators can be detected from the distance of two peaks in the probe spectrum. The study is of great significance to the fields of precision measurement and quantum information processing.

Electrically tunable nanophotonic switch based on graphene–silicon hybrid ring resonator

Electrically tunable nanophotonic switch based on graphene–silicon hybrid ring resonator

Highly Reproducible Heterosynaptic Plasticity Enabled by MoS2/ZrO2-x Heterostructure Memtransistor.

Electrically tunable resistive switching of a polycrystalline MoS2-based memtransistor has attracted a great deal of attention as an essential synaptic component of neuromorphic circuitry because its switching characteristics from the field-induced migration of sulfur defects in the MoS2 grain boundaries can realize multilevel conductance tunability and heterosynaptic functionality. However, reproducible switching properties in the memtransistor are usually disturbed by the considerable difficulty in controlling the concentration and distribution of the intrinsically existing sulfur defects. Herein, we demonstrate reliable heterosynaptic characteristics using a memtransistor device with a MoS2/ZrO2-x heterostructure. Compared to the control device with the MoS2 semiconducting channel, the Schottky barrier height was more effectively modulated by the insertion of the insulating ZrO2-x layer below the MoS2, confirmed by an ultraviolet photoelectron spectroscopy analysis and the corresponding energy-band structures. The MoS2/ZrO2-x memtransistor accomplishes dual-terminal (drain and gate electrode) stimulated multilevel conductance owing to the tunable resistive switching behavior under varying gate voltages. Furthermore, the memtransistor exhibits long-term potentiation/depression endurance cycling over 7000 pulses and stable pulse cycling behavior by the pulse stimulus from different terminal regions. The promising candidate as an essential synaptic component of the MoS2/ZrO2-x memtransistors for neuromorphic systems results from the high recognition accuracy (∼92%) of the deep neural network simulation test, based on the training and inference of handwritten numbers (0-9). The simple memtransistor structure facilitates the implementation of complex neural circuitry.

Sequential and Reversible Phase Transformations in Zero‐Dimensional Organic‐Inorganic Hybrid Sb‐based Halides towards Multiple Emissions

AbstractZero‐dimensional (0D) metal halides have drawn increasing attention due to the attractive structure dependent photoluminescence (PL) properties. Here, we report two new 0D organic–inorganic hybrid Sb‐based halides, (MTP)6SbBr6Sb2Br9⋅H2O (MTP=Methyltriphenylphosphonium, crystal 1) and (MTP)2SbBr5 (crystal 2), featuring a reversible structural phase transformation and tunable orange and red emissions upon dehydration and rehydration of H2O molecules. Intriguingly, a subsequent heat treatment further enables the formation of glassy state (MTP)2SbBr5 (glass 3) with near‐infrared luminescence, moreover, a sequential reverse phase transformation from glass 3 to crystal 2 and 1 is triggered by acetonitrile and water vapor stepwise. The anti‐counterfeiting demo based on the tunable and reversible PL switching is finally achieved and thus the phase structure engineering in 0D metal halides expands their multiple applications in optical fields.

Sequential and Reversible Phase Transformations in Zero-Dimensional Organic-Inorganic Hybrid Sb-based Halides towards Multiple Emissions.

Zero-dimensional (0D) metal halides have drawn increasing attention due to the attractive structure dependent photoluminescence (PL) properties. Here, we report two new 0D organic-inorganic hybrid Sb-based halides, (MTP)6 SbBr6 Sb2 Br9 ⋅H2 O (MTP=Methyltriphenylphosphonium, crystal 1) and (MTP)2 SbBr5 (crystal 2), featuring a reversible structural phase transformation and tunable orange and red emissions upon dehydration and rehydration of H2 O molecules. Intriguingly, a subsequent heat treatment further enables the formation of glassy state (MTP)2 SbBr5 (glass 3) with near-infrared luminescence, moreover, a sequential reverse phase transformation from glass 3 to crystal 2 and 1 is triggered by acetonitrile and water vapor stepwise. The anti-counterfeiting demo based on the tunable and reversible PL switching is finally achieved and thus the phase structure engineering in 0D metal halides expands their multiple applications in optical fields.

Tunable metamaterial absorber based on VO2-graphene

In this paper, a tunable multilayer metamaterial absorber is proposed, which is composed of VO2-graphene mixed structure layer, PDMS dielectric layer, VO2 layer, PDMS dielectric layer and bottom metal film layer. The simulation results show that when VO2 is in the insulating phase and the Fermi level of graphene is 0.9 eV, the absorption peak of 0.75–1.15 THz is generated by the interaction resonance of graphene and bottom metal. When VO2 is in metal phase and the Fermi level of graphene is 0 eV, the absorption peak of 2.5–4.5 THz is generated by the resonance of vanadium dioxide. Therefore, the tunable switching between two different frequency bands can be realized. Moreover, the dual regulation of both vanadium dioxide conductivity and graphene Fermi energy level can also modulate the absorption amplitude and broaden absorption band. In order to explain the mechanism of VO2-graphene on the absorption performance, the electric field distribution and equivalent impedance of the absorber are discussed and analyzed in this paper. In addition, the absorption performances at variable incidence angles for both TE and TM polarizations are investigated and the absorber is insensitive to polarization. Therefore, the absorber has potential application value in the terahertz field.

Optimizing switching of non-linear properties with hyperbolic metamaterials

Hyperbolic metamaterials have been demonstrated to have special potential in their linear response, but the extent of their non-linear response has not been extensively modeled or measured. In this work, novel non-linear behavior of an ITO/SiO2 layered hyperbolic metamaterial is modeled and experimentally confirmed, specifically a change in the sign of the non-linear absorption with intensity. This behavior is tunable and can be achieved with a simple one-dimensional layered design. Fabrication was performed with physical vapor deposition, and measurements were conducted using the Z-scan technique. Potential applications include tunable optical switches, optical limiters, and tunable components of laser sources.

Bending Modulated Ultralarge Magnetoresistance in Flexible La0.67Ba0.33MnO3 Thin Film Based Device.

Magnetoresistance based information devices have attracted much attention due to the ability to utilize spins as information carriers. To promote the magnetoresistance-based devices, ultrahigh magnetoresistance ratios are highly desirable for magnetic sensing, memory, and artificial intelligent devices, etc. However, today the magnetoresistance devices are facing the challenge of limited magnetoresistance ratio, low work temperature, or high magnetic field, which calls for proper theories and mechanisms. To address it, we first introduce the flexible bending-controlled magnetoresistance device based on the La0.67Ba0.33MnO3 film. Due to the anisotropic resistance of the La0.67Ba0.33MnO3 film and the nonlinear amplification effect of the Zener diode, the device has exhibited strong magnetoresistive performance (∼8725% at 1 T, 300 K). Combining the assist from mechanical bending and diode, high magnetic field sensitivity with large magnetoresistance ratio (∼1.7 × 104% at 1 T, 300 K) and low work current (∼0.15 mA) is simultaneously achieved at room temperature, which is over 104 times larger than that of the planar La0.67Ba0.33MnO3 film. Based on the above results, we propose one but not the only possible application as tunable multistage switch. Our findings may pave a strategy to develop flexible diode-enhanced magnetoresistance device with ultrahigh magnetoresistance ratios and bending tunable performances.

Ultrafast All-Optical Polarization Switch Controlled by Optically Excited Picosecond Acoustic Perturbation of Exciton Resonance in Planar Microcavities

All-optical switching of the polarization of exciton polaritons is studied using a picosecond acoustic perturbation of the exciton resonance in high-$Q$ planar $\mathrm{Ga}\mathrm{As}$/$\mathrm{Al}\mathrm{As}$ microcavities. An irreversible switching of the degree of circular polarization from $22\mathrm{%}$ up to $82\mathrm{%}$ is realized in a microcavity pumped by a laser with a photon energy slightly exceeding the lower polariton resonance. The polarization switch is performed by a short-term, about 30-ps-long, blueshift of the exciton energy of ($\mathrm{In},\mathrm{Ga}$)$\mathrm{As}$ quantum wells in the cavity active layer by a 10-ps strain pulse generated in the $\mathrm{Ga}\mathrm{As}$ substrate by a violet femtosecond laser pulse and injected into the microcavity. The proposed all-optical control of light polarization using acoustic modulation of a polariton resonance opens the way for fast and easily tunable optical polarization switches.