Kerr Effect Research Articles

Directly accessing the single-soliton state of a Kerr microcomb and its universal scaling law [Invited

Soliton microcombs have attracted considerable research interest due to their unique properties. Being able to directly access the single-soliton state in a Kerr microresonator simplifies the device operation and may inspire new applications. However, the general conditions leading to such operations are not well understood. In this work, we aim to elucidate the key factors enabling the direct access of the single-soliton state in a Kerr microresonator by combining the experimental results in an integrated silicon carbide platform and a comprehensive analysis based on the normalized Lugiato-Lefever equation. A general criterion linking the Kerr nonlinearity, dispersion, and thermo-optic properties has been derived, which is applicable to Kerr microresonators with varied materials, sizes, optical quality factors, and dispersion.

Magnon-mediated optical frequency comb in a cavity optomagnonical system

Generally, optical frequency combs (OFC) are generated through nonlinear effects in optical pumping, such as Kerr nonlinearity, the electro-optic effect, and second-order nonlinearity. Here, we propose an effective mechanism for generating OFC in a cavity optomagnonical system via the nonlinearity of magnon-photon coupling. Our results demonstrate that robust OFC can be achieved in this system when driven by effective nanosecond pulses in the non-perturbation regime. Notably, the addition of an extra microwave pump field can enhance magnon-photon coupling and reduce the system’s reliance on the optical pump field. Furthermore, the number and spacing of the OFC teeth can be adjusted by selecting appropriate experimental parameters. These findings contribute to a deeper understanding of the quantum and nonlinear properties of magnons and pave the way for the development of OFC devices in integrated optics and photonics.

Ultra‐Broadband Visible‐DUV Supercontinuum Generation by Non‐Resonant Coherent Raman Scattering in Air

AbstractTo date, supercontinuum light in the visible and near‐infrared ranges is readily realizable by the optical Kerr effect through self‐phase modulation of ultrashort laser pulses in transparent media. However, it is still a challenge to extend the supercontinuum spectrum down to the deep‐ultraviolet (DUV) range, which is particularly needed for exploring ultrafast dynamics in chemistry, materials, and biology. Here, an approach of non‐resonant coherent Raman scattering is developed to generate ultra‐broadband visible‐DUV supercontinuum in ambient air with a spectral range spanning over 250 nm and a wavelength down to 220 nm. A rovibrational coherence is established in air molecules by filamentation of a near‐infrared femtosecond 800 nm pulse and two femtosecond Raman laser pulses at 267 and 400 nm are introduced into the coherent media to induce non‐resonant coherent Stokes and anti‐Stokes Raman scatterings, which serve as the spectral bridges to link the neighboring Raman pump laser spectra, resulting in ultra‐broadband supercontinuum light. The mechanism is further verified by examining the broadening of picosecond N2+ laser lines with narrow bandwidths (10–30 cm−1), which forms a supercontinuum spectrum spanning over 150 nm. The work provides a viable route for the establishment of coherent DUV supercontinuum in the gas media at designed wavelength ranges.

Excitonic Effects on the Ultrafast Nonlinear Optical Response of MoS2 and Fluorinated Graphene/MoS2 Heterostructure Films for Photonic Applications.

In the present work, the ultrafast nonlinear optical (NLO) response of some molybdenum disulfide (MoS2), fluorinated graphene (FG), and FG/MoS2 heterostructure thin films was studied using the Z-scan and optical Kerr effect techniques employing femtosecond laser pulses at different excitation wavelengths (i.e., 400, 570, 610, 660, 800, and 1200 nm). The experiments have shown that the NLO response of the MoS2 and MoS2/FG films was significantly enhanced when the films were excited with 400, 610, and 660 nm laser pulses due to resonance effects with the close-lying excitons in these nanostructures. For a better evaluation of the resonant enhancement of the NLO response, measurements were also carried out at off-resonant wavelengths, i.e., at 570, 800, and 1200 nm. The presence of excitons in the MoS2 and MoS2/FG films resulted in strong saturable absorption and self-defocusing, with exceptionally large values of third-order susceptibilities χ(3) ranging from 10-12 to 10-13 esu. In addition, the NLO response of the MoS2/FG heterostructure was found to be stronger than that of the individual MoS2 and FG films, most probably attributed to interlayer carrier transfer. The determined NLO parameters of the studied nanostructures were found to be comparable to, and in some cases exceeded, those of other reported 2D materials known to exhibit a strong NLO response as well. These findings not only advance the fundamental understanding of the contributions of excitons on the NLO response/properties of transition metal dichalcogenide-based ultrathin films but also highlight the importance of excitons for tailoring their NLO response in view of various applications in advanced optoelectronics and photonic devices.

Floquet topological dissipative Kerr solitons and incommensurate frequency combs

Generating coherent optical frequency combs in micro-ring resonators with Kerr nonlinearity has remarkably advanced the fundamental understanding and applications of temporal dissipative solitons. However, the spectrum of such soliton combs is restricted to the conventional definition of combs as phase-locked, equidistant lines in frequency. Here, we introduce a new class of floquet topological soliton combs that emerge in two-dimensional arrays of strongly coupled resonators engineered using floquet topology. Specifically, we demonstrate incommensurate combs where the comb lines are not equidistant but remain phase-locked. These incommensurate combs are generated by self-organized, phase-locked floquet topological soliton molecules that circulate the edge of the array. We show that these floquet topological solitons are robust and they navigate around defects, allowing for agile tunability of the comb line spacing. Our results introduce a new paradigm in using floquet engineering to generate unconventional frequency combs beyond those achievable with single or weakly coupled resonators.

Relationship Between Aberration Coefficients of an Optical Device and Its Focusing Property

The best focus point of a focused Gaussian beam subject to a phase aberration is generally shifted with respect to the focal plane of the focusing lens. This focus shift is attributed to a lensing effect that belongs to the phase aberration, which mean focal length can be determined from the aberration coefficients determined in the framework of a Zernike polynomial decomposition. In this paper, we have checked the validity of this procedure, already available in literature, applied to three aberration types: a pure primary spherical aberration, the Kerr effect induced by a Gaussian beam, and an axicon illuminated by a Gaussian beam. Note that usually, the mean focal length of an aberrated lens is based on the relation between the effective radius of curvature of the wavefront before and after the lens. However, in this paper, the focal length associated with the phase aberration under study is defined from the point of the best focus, where the diffracted intensity on the axis is the maximum.

Generation and enhancement of sum sideband in a magnon Kerr nonlinearity assisted optomechanical system

Abstract A theoretical scheme to enhance the sum sideband generation (SSG) via magnon Kerr nonlinearity assisted optomechanical system is proposed. In this scheme, the yttrium iron garnet sphere is placed within the cavity system and the frequency components are generated at the sum sideband through optomechanical nonlinear interaction and cavity-magnon linear coupling interaction. The results show that the efficiency of SSG can be enhanced by several orders of magnitude, and the gain in SSG efficiency also varies. The dependence of SSG on the system parameters, including the power of the control field, the frequency detuning of the probe fields and the coupling strengths between the optomechanical coupling and the cavity-magnon coupling is analyzed in detail. The change of SSG by varying the optomechanical coupling strength and cavity-magnon coupling strength is also investigated, and it is found that new matching conditions are generated. The enhanced SSG method may have potential application prospects in realizing the measurement of high-precision weak forces, quantum information processing and quantum-sensitive sensing.

Linear and nonlinear coupling of light in twin-resonators with Kerr nonlinearity

Nonlinear effects in microresonators are efficient building blocks for all-optical computing and telecom systems. With the latest advances in microfabrication, coupled microresonators are used in a rapidly growing number of applications. In this work, we investigate the coupling between twin-resonators in the presence of Kerr nonlinearity. We use an experimental setup with controllable coupling between two high-Q resonators and discuss the effects caused by the simultaneous presence of linear and nonlinear coupling between the optical fields. Linear-coupling-induced mode splitting is observed at low input powers, with the controllable coupling leading to a tunable mode splitting. At high input powers, the hybridized resonances show spontaneous symmetry breaking (SSB) effects, in which the optical power is unevenly distributed between the resonators. Our experimental results are supported by a detailed theoretical model of nonlinear twin-resonators. With the recent interest in coupled resonator systems for neuromorphic computing, quantum systems, and optical frequency comb generation, our work provides important insights into the behavior of these systems at high circulating powers.

Higher Harmonic Generation Arising from the Bessel Function Expansions of the Carrier-Envelope-Phase Driven by the Femtosecond Optical Kerr Effect

Higher Harmonic Generation Arising from the Bessel Function Expansions of the Carrier-Envelope-Phase Driven by the Femtosecond Optical Kerr Effect

Recent Progress in Two-Dimensional Magnetic Materials.

The giant magnetoresistance effect in two-dimensional (2D) magnetic materials has sparked substantial interest in various fields; including sensing; data storage; electronics; and spintronics. Their unique 2D layered structures allow for the manifestation of distinctive physical properties and precise performance regulation under different conditions. In this review, we present an overview of this rapidly developing research area. Firstly, these 2D magnetic materials are catalogued according to magnetic coupling types. Then, several vital effects in 2D magnets are highlighted together with theoretical investigation, such as magnetic circular dichroism, magneto-optical Kerr effect, and anomalous Hall effect. After that, we forecast the potential applications of 2D magnetic materials for spintronic devices. Lastly, research advances in the attracting magnons, skyrmions and other spin textures in 2D magnets are discussed.

Magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM) studies on Cr/Ni nanodot arrays deposited using innovative nano-stencil method

AbstractNanodot arrays of Nickel (Ni) on Chromium (Cr), [Cr in two forms i. e. (Cr dot) and Cr (layer)] were fabricated by electron beam evaporation technique using nano-stencil. The deposition of a periodic dot pattern was confirmed through atomic force microscopy (AFM) imaging. The nano magnetic properties of the Cr/Ni nanodot arrays were probed using both Magnetic Force Microscopy (MFM) and Magneto-Optical Kerr Effect (MOKE) magnetometer. MOKE measurements unveiled saturated hysteresis with the exchange bias effect for the in-plane configuration and a minor hysteresis loop for the out-of-plane configuration in the Cr/Ni nanodot system. The experimental results were found to be in good agreement with the theoretical Stoner-Wohlfarth (SW) model. Additionally, the exchange bias effect was also observed in the Cr (thin film)/Ni (nanodot) system for both the in-plane and out-of-plane configurations, showing the dominating behavior of the Cr layer over the Ni dots due to its continuous layer and higher thickness. The observation of exchange bias properties was also verified through MFM measurements conducted with both positive and negative in-plane magnetic fields. Hence, this straightforward nano-stencil method holds significant promise for the streamlined production of patterned AFM/FM arrays enabling the comprehensive study of exchange bias phenomena. The magnetic properties of the Cr/Ni structure can be manipulated by depositing Cr either in nanodot form or in continuous layer form.

Measuring the Electro-Optical Kerr Effect Against the Background of Electro-Absorption Modulation in Liquids.

A new approach to the dynamic polarimetric method is proposed, which allows for the decoupling of electro-optical Kerr effect measurements from the electro-absorption effect in partially transparent liquids. The method is illustrated by using the results of engine oil measurements as a function of temperature and modulating field frequency. It was shown that the birefringence induced in the sample, the modulation of the ordinary wave transmission, and the modulation of the extraordinary wave transmission in the sample can be shifted in phase with respect to the square of the applied alternating modulating field. Each of these three phase shifts can depend differently on the temperature and frequency. Neglecting the influence of electro-absorption on electro-optical measurements in liquids or considering electro-absorption as an effect correlated in phase with induced birefringence may lead to significant measurement errors. This indicates that the Kerr constant and the electro-absorption coefficients for an alternating electric field should be considered as complex quantities instead of real values, as they have been traditionally. The proposed approach fills an important gap in measurement techniques described in the literature, which may provide erroneous results for measurements of the Kerr constant in partially transparent liquids including many industrially important liquids.

Toward tailored light absorption manipulation by Kerr nonlinear nanoslits within a grating Fabry-Perot cavity coupled with reconfigurable GST225 material

In this paper, we investigate the absorption tunability of a silver plasmonic grating incorporating Kerr-type nonlinear graphene-oxide (GO) nanoslits and Ge2Sb2Te5 (GST225) phase-change material at telecom wavelengths. The linear absorption spectra reveal that the amorphous GST225 grating exhibits two distinct absorption peaks, while half-crystallization leads to a single pronounced peak, and full crystallization results in a redshifted peak with a slightly decreased value. These findings confirm that the crystalline degree of GST225 significantly modulates the absorption characteristics. Upon exposure to a nanosecond Gaussian pulse laser irradiation with appropriate fluences, the electric field confinement within the nanoslits intensifies, particularly at the center of the pulse, leading to a pronounced absorption adjustment due to Kerr nonlinearity. Temporal examination at the L-band wavelength of 1591.5 nm reveals a U-shaped absorption response for both amorphous and crystalline GST225, with a pronounced dip at the pulse’s peak. In the half-crystallized state, the weak linear absorption can be substantially enhanced at both the leading and trailing edges of the pulse, with a dip at the center, illustrating the Kerr nonlinearity within the GO nanoslits. The dynamic behavior of absorption under different laser fluences underscores the potential of this system for high-contrast optical switching. Our results offer insights into the development of reconfigurable optical switches utilizing nonlinear Kerr effects, paving the way for advancements in tunable optical communication technologies.

Evidence of 1+1D Photorefractive Stripe Solitons Deep in the Kerr Limit.

The Kerr nonlinearity allows for exact analytic soliton solutions in 1+1D. While nothing excludes that these solitons form in naturally occurring real-world 3D settings as solitary walls or stripes, their observation had previously been considered unfeasible because of the strong transverse instability intrinsic to the extended nonlinear perturbation. We report the observation of solitons that are fully compatible with the 1+1D Kerr paradigm limit hosted in a 2+1D system. The waves are stripe spatial solitons in bulk copper doped potassium-lithium-tantalate-niobate (KLTN) supported by unsaturated photorefractive screening nonlinearity. The parameters of the stripe solitons fit well, in the whole existence domain, with the 1+1D existence curve that we derive for the first time in closed form starting from the saturable model of propagation. Transverse instability, that accompanies the solitons embedded in the 3D system, is found to have a gain length much longer than the crystal. Findings establish our system as a versatile platform for investigating exact soliton solutions in bulk settings and in exploring the role of dimensionality at the transition from integrable to nonintegrable regimes of propagation.

Enhancement of transverse magneto-optical Kerr effect using transition metals in a grating-based gyro-electric structure

Abstract This study proposes a new structure based on a grating with magneto-optical properties and a layer of transition metals (platinum, silver, copper, gold, and palladium). The research aims to investigate the impact of surface plasmon polaritons on enhancing the transverse magneto-optical Kerr effect when exposed to TM- and TE-polarized waves. After optimizing the structure’s dimensions, it was determined that the transition metal layer should have a thickness of 20 nm. The study involves applying TM- and TE-polarized light to the structure to observe variations in reflected light and the transverse magneto-optical Kerr effect. The findings reveal that the gyro-electric magneto-optics material responds to TMpolarized waves, and silver and gold are identified as the most effective metals for the proposed structure.

Dynamical evolution of a five-level atom interacting with an intensity-dependent coupling regime influenced by a nonlinear Kerr-like medium

We present an analytical solution for a quantum system characterized by a double Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda$$\\end{document} five-level atom interacting with an intensity-dependent coupling regime, influenced by a nonlinear Kerr-like medium. We also derive the constants of motion through Heisenberg’s equations. Furthermore, the dynamical evolution of the entanglement and quantum coherence between the atom and the field is discussed using linear entropy and l1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$l_{1}$$\\end{document}-norm of coherence. Through a comprehensive examination of the quantum system, it is observed that both the detuning and the Kerr-like parameters exert a significant impact on the degree of entanglement and coherence. However, the impacts of detuning and the Kerr effect become less pronounced when the photon multiplicity is high. In addition, we conduct a comparison between the five-level atomic system and a four-level system, revealing that the number of energy levels has a profound impact on the behavior of entanglement and coherence. These findings highlight the importance of atomic structure and photon multiplicity in controlling and optimizing quantum processes, particularly in applications involving quantum communication and information processing.

Pure-quartic solitons with PT-symmetric nonlinearity.

We propose a new, to the best of our knowledge, class of soliton based on the interaction of parity-time (PT) symmetric nonlinearity and quartic dispersion or diffraction. This novel kind of soliton is related to the recently discovered pure-quartic solitons (PQS), which arise from the balance of the Kerr nonlinearity and quartic dispersion, through a complex coordinate shift. We find that the PT-symmetric pure-quartic soliton presents important differences with respect to its Hermitian (Kerr) counterpart, including a nontrivial phase structure, a skewed spectral intensity, and a higher power for the same propagation constant. Further analysis reveals these solitons are linearly stable.

Light bullets under conditions of third harmonics generation

Abstract An analytical study of the possibility of a two-color light bullet forming during generation of the third harmonics in a graded index waveguide with the focusing Kerr nonlinearity is carried out. It is shown that under conditions of phase and group matching, as well as the absence of group velocity dispersion at the third harmonic frequency, a stable light bullet can be formed under certain restrictions. This applies to the lower limit on the temporal duration of the light bullet and to the upper limit on its power. The most stringent condition is the double restriction on the transverse radius of the light bullet.

The role of Rh spacer layer thickness on the noncollinear interlayer exchange coupling

Abstract The relationship between noncollinear interlayer exchange coupling (IEC) and magnetic anisotropic behavior in Fe/Rh/Fe trilayers is studied in detail by using magneto-optical Kerr effect (MOKE) and anisotropic magnetoresistance (AMR) techniques. It is found that the Rh spacer layer thickness strongly affects IEC and magnetic anisotropy in these trilayers. The role of Rh spacer layer thickness is shown in the oscillatory behavior in the magnitude of the magnetic anisotropy, the transition from uniaxial to four-fold anisotropy, the shift of easy axis for magnetic anisotropy, and the unusual increase in the sheet resistance. As an outcome of this study, we discuss the underlying mechanism based on the noncollinear IEC across the Fe/Rh/Fe interlayer. As a result, it has been shown that the noncollinear IEC can be controlled by the various Rh spacer thicknesses among nonmagnetic transition layers.

Nonlinear Thermoplasmonics in Graphene Nanostructures.

The linear electronic dispersion relation of graphene endows the atomically thin carbon layer with a large intrinsic optical nonlinearity, with regard to both parametric and photothermal processes. While plasmons in graphene nanostructures can further enhance nonlinear optical phenomena, boosting resonances to the technologically relevant mid- and near-infrared (IR) spectral regimes necessitates patterning on ∼10 nm length scales, for which quantum finite-size effects play a crucial role. Here we show that thermoplasmons in narrow graphene nanoribbons can be activated at mid- and near-IR frequencies with moderate absorbed energy density, and furthermore can drive substantial third-harmonic generation and optical Kerr nonlinearities. Our findings suggest that photothermal excitation by ultrashort optical pulses offers a promising approach to enable nonlinear plasmonic phenomena in nanostructured graphene that avoids potentially invasive electrical gating schemes and excessive charge carrier doping levels.