Nonlinear Devices Research Articles

All-optical switching based on spatial self-phase modulation of Ag/violet phosphorus heterojunctions.

With the increasing demand for high-performance passive nonlinear photonic devices, significant progress has been made in spatial self-phase modulation (SSPM) based on 2D nanomaterials in all-optical switches, logic gates, and information converters in recent years. However, there are still challenges in improving the responsiveness of photonic devices. In this work, we prepared a heterojunction of Ag nanoparticles deposited on the surface of violet phosphorus nanosheets (VP Ns), investigated their SSPM, and demonstrated their performance in all-optical switches. The SSPM experimental results show that compared with pure VP Ns at the same light intensity, both the maximum number and the formation time of self-diffraction rings in Ag/VP heterojunctions increase, and the nonlinear refractive index is approximately doubled. The main reason for optical nonlinearity enhancement is that the internal electric field in the heterojunction strengthens the mobility of the photogenerated carrier, thereby enhancing its optical nonlinearity. In particular, we demonstrate the performance of all-optical switches based on SSPM by utilizing the superior optical nonlinearity of Ag/VP heterojunctions. It is shown that with the increase of low-dose Ag content in heterojunctions, the switching time in the all-optical switch becomes shorter and the maximum number of self-diffraction rings of the signal light increases, although the quality of self-diffraction rings slightly decreases due to the scattering of Ag particles. The results contribute to the design and implementation of high-performance nonlinear photonic devices, based on the use of heterojunctions with low-cost preparation and a high nonlinear refractive index.

Comparison of the effectiveness of stabilizing quasi-resonant and inertial influences on the parameters of a controlled Lorentz system with dynamic chaos

Problem statement. The article is devoted to determining the comparative energy efficiency of stabilizing quasi-resonant and inertial effects on the parameters of a controlled discrete-nonlinear Lorentz system with dynamic chaos. Currently, information transmission systems based on the use of chaotic dynamics effects are developing extremely intensively. The need to ensure reproducibility of parameters and statistical characteristics of pseudorandom signals generated on the basis of nonlinear systems with dynamic chaos makes the task of stabilizing chaotic modes of nonlinear devices and systems urgent. Goal. Determination of the comparative energy efficiency of stabilizing quasi-resonant and inertial effects on the parameters of a controlled discrete-nonlinear Lorentz system with dynamic chaos. Results. It is shown that fluctuations causing deviations of the discrete-nonlinear Lorentz system from equilibrium states lead to changes in the quasi-resonant frequency and the effectiveness of inertial stabilizing effects. It is established that the effectiveness of stabilizing inertial effects on parameter b of a controlled discrete-nonlinear Lorentz system increases with an increase in the fluctuation deviation of the system from equilibrium states. The conditions under which stabilizing inertial effects become energetically more advantageous than quasi-stationary effects on the parameters of a discrete-nonlinear system are determined. Practical significance. Ensuring the required regular behavior with the transfer of nonlinear electronic and quantum devices and systems from stochastic to regular mode.

Analysis of Sinusoid Plus Random Telegraph Noise in Nonlinear Devices: Series Characteristic Function Method

Analysis of Sinusoid Plus Random Telegraph Noise in Nonlinear Devices: Series Characteristic Function Method

Plasmon-enhanced second harmonic generation of metal nanostructures.

As the most common nonlinear optical process, second harmonic generation (SHG) has important application value in the field of nanophotonics. With the rapid development of metal nanomaterial processing and chemical preparation technology, various structures based on metal nanoparticles have been used to achieve the enhancement and modulation of SHG. In the field of nonlinear optics, plasmonic metal nanostructures have become potential candidates for nonlinear optoelectronic devices because of their highly adjustable physical characteristics. In this article, first, the basic optical principles of SHG and the source of surface symmetry breaking in metal nanoparticles are briefly introduced. Next, the related reports on SHG in metal nanostructures are reviewed from three aspects: the enhancement of SHG efficiency by double resonance structures, the SHG effect based on magnetic resonance and the harmonic energy transfer. Then, the applications of SHG in the sensing, imaging and in situ monitoring of metal nanostructures are summarized. Future opportunities for SHG in composite systems composed of metal nanostructures and two-dimensional materials are also proposed.

Nonlinear Microwave Device LabVIEW Automatic Test Bench: Double-frequency IMD3 Characterization

Nonlinear Microwave Device LabVIEW Automatic Test Bench: Double-frequency IMD3 Characterization

Broad -band nonlinear optical response in Bi2Te0.6S2.4 alloys based on alloy engineering.

Alloy engineering plays an important role in regulating the optoelectronic properties of materials. This work demonstrates that Bi2Te0.6S2.4 alloys can extend nonlinear optical response to the near-infrared range. Te alloying at S sites can narrow the band gap, as proved by density functional theory (DFT) calculations, leading to a broadband saturable absorption response ranging from ultraviolet (350 nm) to near-infrared (1100 nm) wavelength with negative nonlinear optical absorption coefficient ranging from -0.12 cm GW-1 to -1.28 cm GW-1. Moreover, the broadband carrier dynamic of Bi2Te0.6S2.4 alloys was investigated via femtosecond transient absorption (TA) at an excitation of 325 nm. A faster carrier dynamic at near-infrared wavelength was observed because of an increase in electron density at the conduction band minimum due to the additional Bi-Te interaction, which was corroborated by DFT calculations. These results suggest that alloy engineering provides an effective way for the development of broadband nonlinear optical devices.

Multiwavelength Quantum Correlated Photon Pair Generation for Quantum Entanglement Key Distribution

With the rapid advancement of quantum information technology, fully connected multi-user quantum entanglement distribution networks have garnered increasing attention. Among these, multi-wavelength quantum light sources are key devices for establishing connections between multiple users. Despite recent impressive advances, it remains challenging to increase the wavelength number of photon pairs due to limitations in the design and fabrication of nonlinear optical devices. This work explores the potential of silicon nitride (Si<sub>3</sub>N<sub>4</sub>) microring resonators (MRRs) as scalable platforms for multi-wavelength quantum light sources.<br>In this work, we conduct a comprehensive analysis of the key design parameters of the Si<sub>3</sub>N<sub>4</sub> MRRs, including waveguide dimension, resonator dispersion, and coupling condition, to optimize photon-pair generation. Based on these parameters, a Si<sub>3</sub>N<sub>4</sub> MRR with a free spectral range of 20 GHz and an average quality factor of 1.6 million is designed and fabricated. This small free spectral range enables the generation of more channels of correlated photon pairs using the same wavelength resources. The high-quality of the resonator facilitates the high photon pair generation rate, which are critical for quantum entanglement distribution. With a continuous-wave pump laser, correlated photon pairs across a wide spectral range are generated through the spontaneous four-wave mixing (SFWM). The coincidence-to-accidental ratio (CAR) measurements verify the strong quantum correlation between photon pairs, highlighting the reliability of the system for entanglement distribution. Furthermore, the generation and output characteristics of quantum-correlated photon pairs are experimentally investigated with a tunable bandpass filter. The results demonstrate that the successful generation of 71 wavelength-correlated photon pairs within a 25.6 nm spectral range is achieved as shown in the Figure A. Our results pave the way for the development of multi-wavelength quantum light sources with Si<sub>3</sub>N<sub>4</sub> platform, thereby advancing the multi-user quantum networks.

Features of the formation of nickel-containing nanoparticles on glassy carbon electrodes using electrodeposition from solutions of sodium pectate complexes

Problem statement. Currently, many leading companies in the field of electronics, radio engineering, and aerotechnics are concerned about the depletion of non-renewable resources such as platinum, gold, silver, indium and even the more common lithium, nickel and copper, which they actively use in their products. The design and synthesis of nanostructures with controlled morphology has attracted the attention of many researchers and engineers, since it is much more efficient to deposit a small amount of metal on the surface being used than to create a part entirely from this metal. There are several main methods for producing nanostructures on a surface: chemical deposition, electron beam lithography, pulsed laser deposition, electrochemical deposition and other methods. Electrochemical deposition is worth highlighting among all methods, because it makes it possible to obtain such surfaces relatively cheaply and on a large scale and control their morphology by changing deposition conditions, such as time, potential, solution pH, etc. Purpose of the study. Obtain nickel-containing nanoparticles on glassy carbon by electrodeposition from an aqueous solution of biopolymer complexes of sodium pectate with divalent nickel; to determine the influence of electrodeposition conditions, namely, the duration of deposition and the content of Ni(II) ions in sodium petectate complexes, on the morphology of the resulting surface. Results. Studies have been carried out of the influence of electrodeposition conditions on the morphology of the resulting glassy carbon electrode surface. It was found that biopolymer ligands act as a stabilizing agent for the formation of nickel-containing nanoparticles instead of a nickel-containing layer. The standard sizes of the resulting nanoparticles are in the range of 20 – 90 nm. The nickel content in the complexes, as well as the deposition time, proportionally affects the amount of deposited nanoparticles, but has little effect on their sizes. Practical significance. The results obtained make it possible to use them for controlled electrodeposition of nickel-containing nanoparticles on conducting surfaces in the development of nonlinear optical devices, LEDs, diodes, transistors, logic gates, sensors and other electronic devices.

Broadband and weak-dispersion nonlinear response enhancement in the epsilon-near-zero region of a nano-stepped metasurface.

Optical media with dispersion-free large nonlinearity are highly desired for a broad range of applications, such as spectroscopy, all-optical data processing, and quantum information. Here, we report that a metasurface composed of an indium-tin-oxide nano-step array can exhibit weak-dispersion and enhanced optical nonlinearity theoretically in the region of the spectrum where the real part of its effective permittivity is close to zero. Such nonlinear features are attributed to the offset of the structural dispersion and material dispersion of the metasurface in its epsilon-near-zero region. The nonlinear refractive index of our metasurface remains at around n2 = 1.5 × 10-2 cm2 GW-1 in a wide wavelength range from 1300 to 1510 nm, and the nonlinear absorption coefficient is greater than 1 × 105 cm GW-1 in the range from 1280 to 1780 nm in simulation. Our results open a novel approach to applications of nonlinear photonic devices requiring high integration density and stable performance.

Nonlinear squeezing of stochastic motion

Linearized stochastic nanomechanical systems operating at nonzero temperatures and constant frequency and damping are restricted in their capacity to reduce noise in nonlinear combinations of the canonical variables. Nonlinear dynamics are then required in order to overcome these limits. Here we demonstrate how to make these limits explicit in the form of a threshold for nonlinear squeezing of the motional variables. Noise suppression below the threshold cannot be explained by linearized dynamics and is helpful in low-noise nonlinear devices at an ambient temperature. We predict that a state of the art levitating particle, exposed to cubic or quartic trapping potentials for a short interval will display nonlinear squeezing of stochastic motion that cannot be replicated by linear motion.

Bound states in continuum domain of double resonant ring metal metasurfaces

Metasurfaces have found extensive applications in microwave, terahertz, and optical range, serving different purposes such as filters, sensors, slow light devices, and nonlinear devices due to their distinctive electromagnetic response characteristics. Recent development requires metasurface devices to exhibit enhanced monochromaticity and stronger light interaction. Consequently, there is a growing interest in designing metasurfaces with high-quality factor (<i>Q</i>-factor) resonances, considering their crucial role in achieving sharp resonances through constructing bound states in the continuum (BIC) mode. The utilization of BIC has emerged as a prominent method of designing metasurfaces with high <i>Q</i>-factor resonances. Due to the fact that the changes in the structural parameters of metasurfaces can simultaneously affect the resonance of two components of q-BICs, it is difficult to achieve on-demand design of operating frequency, bandwidth, and <i>Q</i>-factor. In this work, we investigate a novel THz metasurfaces supporting q-BIC resonance. We optimize the geometric parameters of two split ring resonators (SRRs) to tailor the operating frequencies of intrinsic resonance, and tune the coupling between different resonance modes to form the q-BIC mode resonance. The dominant modes are demonstrated by the results of multipolar decomposition calculations of the electromagnetic field distributions and scattered power at different resonant operating frequencies. In <i>x</i>-polarized and <i>y</i>-polarized incident electromagnetic wave, the normalized coupling strength ratio between the two modes are calculated by Jaynes-Cummings model to be 0.54% (<i>x-</i>polarized) and 4.42% (<i>y-</i>polarized) respectively, which explains the law that the resonant frequency of different modes changes with the structural parameters of SRRs device. In order to analyze the refractive index sensing capabilities of our designed metasurfaces under the incident electromagnetic waves with different polarizations, we investigate the variations of the transmitted spectrum of the metasurface with refractive index of matters. The calculated results show that the sensitivity of the metasurface is 151 GHz/RIU when the incident wave is <i>y</i>-polarized and 108 GHz/RIU when the incident wave is <i>x</i>-polarized. We realize the effective control of the operating frequency, bandwidth, and <i>Q</i>-factor of the q-BIC mode resonance in the transmission spectrum of the metasurface, which provides a new idea for the practical designing of terahertz metasurfaces with high <i>Q</i>-factor.

Theoretical study on photoinduced charge transfer in one-photon and two-photon absorption of branching oligofluorenes

Oligofluorenes have been identified as very promising two-photon absorption (TPA) materials and present great application potential for the fabrication of nonlinear optical devices, but the TPA mechanism and corresponding electron excitation properties have not been studied. Here, the photoinduced charge transfer characteristics of V-shaped and Y-shaped branching oligofluorenes that consist of two and three fluorene units in each branch during one-photon absorption (OPA) and TPA processes are analyzed theoretically using the density functional theory and visualization sum-over-states model. The calculated results show that the OPA intensity and TPA cross-section are significantly enhanced by increasing the branch length or changing the structure from V-shaped to Y-shaped. The long-distance charge transfer only occurs on the second transition of TPA at high excited states. Compared to Y-shaped molecules, V-shaped structures exhibit a stronger cooperative effect among the different branches.

Multivariable Fractional-Order Controller Design for a Nonlinear Dual-Tank Device

Fractional calculus is defined by expanded integer order integration and differentiation. In this paper, multiple mathematical models of a nonlinear dual-tank device are precisely formulated by fractional calculus. Using the accurate model, a multivariable fractional-order controller is designed for nonlinear devices. The merits of the fractional-order design include: (1) control of multivariable nonlinearities, (2) compensation of uncertainties, and (3) elimination of coupling effects. Simulations and experiments are conducted to verify the precision of the fractional order models and the effectiveness of the multivariable fractional-order control system design.

Electrically Tunable Strong Optical Nonlinearity in Near‐Infrared by Coupled Metallic Quantum Wells

AbstractAn electrically tunable nonlinear optical device working at near‐infrared wavelength is theoretically and experimentally demonstrated. Ultrahigh optical second‐order nonlinearity from titanium‐nitride‐based coupled metallic quantum wells can be electrically tuned by external electric field. Tunability of second‐order susceptibility χ(2) reaches a 63% modulation depth with an average tunability of 10.5% per volt. In addition, electro‐optic modulation of second‐harmonic signal is presented by continuous tuning of χ(2) over a long period of time with high stability. These results provide a new material platform with actively controllable strong nonlinearity for future nonlinear photonic systems, such as ultra‐compact opto‐electronic modulation devices and reconfigurable nonlinear metamaterials and metasurfaces.

The Influence of Electrochemical Bias on the Exciton Dynamics of MoS2 thin Films

2D transition metal dichalcogenides are an attractive family of materials in the field of electronics and optoelectronics. They are excellent candidates for sensitive photodetectors, light harvesting devices (photovoltaics, photocatalysts or photoelectrodes), lasers or non-linear optical devices. All these applications rely on light-matter interactions, which processes will ultimately decide the efficiency of the derived devices. Understanding carrier dynamics and the interaction of various exotic quasi-particles (excitons, trions) in these materials is of paramount importance to design better performing devices.Pump-probe transient absorption/reflection spectroscopy (TAS/TRS) is a powerful technique to study photophysical processes involved in charge carrier generation and recombination on the ultrafast timescale. In MoS2 photoelectrodes after light excitation different types of excitons are generated, and their decay can be monitored with these techniques. Coupling electrochemical techniques with these ultrafast methods, allows to probe the decay of the excited state in these materials under working conditions. In this manner the effect of trap state filling [1] or the effect of charge extraction [2] on the charge carrier dynamics of photoelectrochemical systems can be revealed.In my presentation I will show ultrafast spectroelectrochemical measurements on ITO/MoS2 photoelectrodes and reveal how the decay of excitons are influenced by the applied electrochemical bias. By comparing results from TAS/TRS spectroscopy the separation of carrier dynamics on the surface and bulk of these systems can be performed. These measurements reveal that the dissociation of excitons occurs at the ITO/MoS2 interface, resulting in a long living exciton population on the surface of these samples. Charging/discharging studies carried out in these systems reveal that the trap states involved in the dissociation of excitons in these systems can be permanently filled. The electrochemical filling of these trap states allows the tuning of the excited state lifetime of these systems, which can aid the better design of photoelectrochemical devices based on MoS2.

Additively Manufactured Wireless Sensors for Rugged IoT, Structural Health Monitoring, Smart Agriculture and Smart Cities Applications

In this talk, inkjet-/3D-printed antennas, interconnects, ‘smart’ encapsulation and packages, RF electronics, microfluidics and sensors fabricated on glass, PET, paper and other flexible substrates are introduced as a system-level solution for ultra-low-cost mass production of Millimeter-Wave Modules for Communication, Energy Harvesting and Sensing applications. Prof. Tentzeris will touch up the state-of-the-art area of fully-integrated printable broadband wireless modules covering characterization of 3D printed materials up to E-band, novel printable ‘ramp’ interconnects and cavities for IC embedding as well as printable structures for self-diagnostic and anti-counterfeiting packages. The presented approach could potentially set the foundation for the truly convergent wireless sensor ad-hoc networks of the future with enhanced cognitive intelligence and ‘rugged’ packaging. Prof. Tentzeris will discuss issues concerning the power sources of ‘near-perpetual’ RF modules, including flexible miniaturized batteries as well as power-scavenging approaches involving thermal, EM, vibration and solar energy forms. The final step of the presentation will involve examples from shape-changing 4D-printed (origami) packages, reflectarrays and mmW wearable (e.g. biomonitoring) antennas and RF modules. Special attention will be paid on the integration of ultrabroadband (Gb/sec) inkjet-printed nanotechnology-based backscattering communication modules as well as miniaturized printable wireless (e.g.CNT) sensors for Internet of Things (IoT), 5G and smart agriculture/biomonitoring applications. It has to be noted that the talk will review and present challenges for inkjet-printed organic active and nonlinear devices as well as future directions in the area of environmentally-friendly (‘green’) RF electronics and ‘smart-skin’ conformal sensors.

From Solution to Surface: Persistence of the Diradical Character of a Diindenoanthracene Derivative on a Metallic Substrate.

Organic diradicals are envisioned as elementary building blocks for designing a new generation of spintronic devices and have been used in constructing prototypical field effect transistors and nonlinear optical devices. Open-shell systems, however, are also reactive, thus requiring design strategies to "protect" their radical character from the environment, especially when they are embedded in solid-state devices. Here, we report the persistence on a metallic surface of the diradical character of a diindeno[b,i]anthracene (DIAn) core protected by bulky end-groups. Our scanning tunneling spectroscopy measurements on single-molecules detected singlet-triplet excitations that were absent for DIAn species packed in assembled structures. Density functional theory simulations unravel that the molecular geometry on the metal substrate can crucially modify the value of the singlet-triplet gap via the delocalization of the radical sites. The persistence of the diradical character over metallic substrates is a promising finding for integrating radical-based materials into functional devices.

Synthesis, growth, and optical applications of N, N′-bis (2-aminophenyl) ethane-1,2-diammonium picrate: An organic crystal

Futuristic organic nonlinear optical single AEDP crystal bearing the IUPAC nomenclature of N, N′-Bis(2-Aminoethyl) Ethane-1,2-Diammonium Picrate was grown via slow evaporation approach in aqueous solvent. The single crystal X-ray diffraction studies were employed for resolving lattice parameters of AEDP single crystal. The data regarding triclinic crystalline structure, bonds vibrations and symmetries of molecular vibrations of the prepared single crystal were realized adopting XRD, FT-IR and vibrational measurements techniques respectively. Evidences regarding excellent crystal optical transparency and maximum crystal non-linear optical properties for the prepared AEDP crystal in the range 200–2000 nm were revealed by Optical absorbance spectrum documented in the UV–vis–NIR wavelength range enhances the scope of unearthing and evolving potential nonlinear systems. Thermal stability and nonlinear optical (NLO) nature of AEDP crystal were inspected by applying differential thermal-thermo gravimetric analysis (DTA–TGA) and second harmonic generation test respectively. The promising features of the crystal leads towards application in the design of nonlinear optical devices and light-controlled electrical switches.

Highly efficient nonlinear vortex beam generation by using a compact nonlinear fork grating

Vortex beams with an orbital angular momentum (OAM) are extremely important in optical trapping, optical micromachining, high-capacity optical communications, and quantum optics. Nonlinear generation of such a vortex beam enables vortex beams to be obtained at new wavelengths, which opens up new possibilities for all-optical switching and manipulation of vortex beams. However, previous nonlinear vortex beam generation suffers from either low efficiency or low-level integration. Here, we use the technique of ultraviolet photolithography-assisted inductively coupled plasma (ICP) etching to realize a compact nonlinear fork grating for high-efficiency nonlinear vortex beam generation. In our experiment, the depth of such a compact nonlinear fork-grating structure can be precisely controlled by etching time. The vortex beams with a topological charge of l = ±1, ± 2, ± 3 can be generated in the far field, and the normalized nonlinear conversion efficiency of such nonlinear vortex beam is 189% W−1cm−2. Our method not only provides an efficient and compact method for nonlinear vortex beam manipulation but also suits for timesaving and large-area nonlinear functional device fabrication.

Enhanced second-harmonic generation in a photonic crystal waveguide-coupled nanocavity using a wavelength-selective reflector

Photonic crystal waveguide-coupled photonic nanocavities are promising to develop integrated nonlinear nanophotonic devices because of their strong nonlinear optical process in cavities with high quality (Q) factors and small modal volume, multiple-wavelength-channel operation, and efficient and highly dense integration with other optical components. However, the intrinsic features of the standing-wave mode in the photonic crystal resonant cavity cause some waveguided light to pass through the nanocavity without coupling, which remains a significant challenge in achieving high nonlinear optical efficiency in integrated nanophotonic devices. To feed back the uncoupled light into the nanocavity and enhance the nonlinear optical efficiency in a photonic crystal waveguide-coupled nanocavity, we designed and fabricated a wavelength-selective reflector based on a silicon carbide two-dimensional photonic crystal structure and experimentally demonstrated the significant enhancement of second harmonic generation (SHG) using the reflector. The findings suggest that the reflector increases the electric field intensity in the nanocavity and improves Q-matching between the nanocavity and the waveguide. These two effects of the reflector significantly enhance the SHG efficiency by 11.5 compared to that without a reflector. The experimental results agree well with the calculation results obtained using coupled-mode theory. Our study paves the way for developing efficient nonlinear optical devices for high-density integrated nanophotonics and quantum applications.