Showing papers on "Kerr effect published in 2022"

All-optical logic devices based on black arsenic–phosphorus with strong nonlinear optical response and high stability

Abstract: The Kerr nonlinearity in two-dimensional (2D) nanomaterials is emerging as an appealing and intriguing research area due to their prominent light processing, modulation, and manipulation abilities. In this contribution, 2D black arsenicphosphorus (B-AsP) nanosheets (NSs) were applied in nonlinear photonic devices based on spatial self-phase modulation (SSPM) method. By applying the Kerr nonlinearity in 2D B-AsP, an all-optical phase-modulated system is proposed to realize the functions of “on” and “off” in all-optical switching. By using the same all-optical phase-modulated system, another optical logic gate is proposed, and the logical “or” function is obtained based on the 2D B-AsP NSs dispersions. Moreover, by using the SSPM method, a 2D B-AsP/SnS2 hybrid structure is fabricated, and the result illustrates that the hybrid structure possesses the ability of the unidirectional nonlinear excitation, which helps in obtaining the function of spatial asymmetric light propagation. This function is considered an important prerequisite for the realization of diode functionalization, which is believed to be a factor in important basis for the design of isolators as well. The initial investigations indicate that 2D B-AsP is applicable for designing optical logical devices, which can be considered as an important development in all-optical information processing.

Mechanical Bistability in Kerr-modified Cavity Magnomechanics

Abstract: Bistable mechanical vibration is observed in a cavity magnomechanical system, which consists of a microwave cavity mode, a magnon mode, and a mechanical vibration mode of a ferrimagnetic yttrium-iron-garnet (YIG) sphere. The bistability manifests itself in both the mechanical frequency and linewidth under a strong microwave drive field, which simultaneously activates three different kinds of nonlinearities, namely, magnetostriction, magnon self-Kerr, and magnon-phonon cross-Kerr nonlinearities. The magnon-phonon cross-Kerr nonlinearity is first predicted and measured in magnomechanics. The system enters a regime where Kerr-type nonlinearities strongly modify the conventional cavity magnomechanics that possesses only a radiation-pressure-like magnomechanical coupling. Three different kinds of nonlinearities are identified and distinguished in the experiment. Our work demonstrates a new mechanism for achieving mechanical bistability by combining magnetostriction and Kerr-type nonlinearities, and indicates that such Kerr-modified cavity magnomechanics provides a unique platform for studying many distinct nonlinearities in a single experiment.

Optical solitons with perturbed complex Ginzburg–Landau equation in kerr and cubic–quintic–septic nonlinearity

Abstract: This paper secures exact solutions from perturbed complex Ginzburg–Landau equation that is taken into account with Kerr law and cubic–quintic–septic nonlinearity. Two approaches are used, namely the trial equation method and complete discriminant system for polynomial method. The abundant exact solutions obtained can better analyze the complex optical phenomena and further demonstrate their essence.

Spectroscopic observation of the crossover from a classical Duffing oscillator to a Kerr parametric oscillator

Abstract: We study microwave response of a Josephson parametric oscillator consisting of a superconducting transmission-line resonator with an embedded DC-superconducting quantum interference device (-SQUID). The DC-SQUID allows to control the magnitude of a Kerr nonlinearity over the ranges where it is smaller or larger than the photon loss rate. Spectroscopy measurements reveal the change in the microwave response from a classical Duffing oscillator to a Kerr parametric oscillator in a single device. In the single-photon Kerr regime, we observe parametric oscillations with a well-defined phase of either 0 or $\ensuremath{\pi}$, whose probability can be controlled by an externally injected signal.

Enhanced self-phase modulation in silicon nitride waveguides integrated with 2D graphene oxide films

Abstract: We experimentally demonstrate enhanced self-phase modulation (SPM) in silicon nitride (Si3N4) waveguides integrated with 2D graphene oxide (GO) films. GO films are integrated onto Si3N4 waveguides using a solution-based, transfer-free coating method that enables precise control of the film thickness. Detailed SPM measurements are carried out using both picosecond and femtosecond optical pulses. Owing to the high Kerr nonlinearity of GO, the hybrid waveguides show significantly improved spectral broadening compared to the uncoated waveguide, achieving a broadening factor of up to ~3.4 for a device with 2 layers of GO. By fitting the experimental results with theory, we obtain an improvement in the waveguide nonlinear parameter by a factor of up to 18.4 and a Kerr coefficient (n2) of GO that is about 5 orders of magnitude higher than Si3N4. Finally, we provide a theoretical analysis for the influence of GO film length, coating position, and its saturable absorption on the SPM performance. These results verify the effectiveness of on-chip integrating 2D GO films to enhance the nonlinear optical performance of Si3N4 devices.

Monolithic Kerr and electro-optic hybrid microcombs

Abstract: Advances in microresonator-based soliton generation promise chip-scale integration of optical frequency comb for applications spanning from time keeping to frequency synthesis. Miniaturized cavities harness Kerr nonlinearity and enable terahertz soliton repetition rates. However, such high repetition rates are not amenable to direct electronic detection. Here, we demonstrate hybrid Kerr and electro-optic microcombs using the lithium niobate thin film that exhibits both Kerr and Pockels nonlinearities. By interleaving the high-repetition-rate Kerr soliton comb with the lowrepetition-rate electro-optic comb on the same waveguide, the wide Kerr soliton mode spacing is divided within a single chip, allowing for subsequent electronic detection and feedback control of the soliton repetition rate. Our work establishes an integrated electronic interface to Kerr solitons of terahertz repetition rates, paving the path towards chipscale optical-to-microwave frequency division and comb locking.

Observation of domain structure in non-collinear antiferromagnetic Mn₃Sn thin films by magneto-optical Kerr effect

Abstract: We perform hysteresis-loop measurement and domain imaging for [Formula: see text]-oriented D0 19 -Mn 3+ x Sn 1- x ([Formula: see text]) thin films using the magneto-optical Kerr effect (MOKE) and compare it with the anomalous Hall effect (AHE) measurement. We obtain a large Kerr rotation angle of 10 mdeg, comparable with bulk single-crystal Mn 3 Sn. The composition x dependence of AHE and MOKE shows a similar trend, suggesting the same origin, i.e., the non-vanishing Berry curvature in the momentum space. Magnetic domain observation at the saturated state shows that x dependence of AHE and MOKE is explained by the amount of the reversible area that crucially depends on the crystalline structure of the film. Furthermore, in-depth observation of the reversal process reveals that the reversal starts with nucleation of sub-micrometer-scale domains dispersed in the film, followed by domain expansion, where the domain wall preferentially propagates along the [Formula: see text] direction. Our study provides a basic understanding of the spatial evolution of the reversal of the chiral-spin structure in non-collinear antiferromagnetic thin films.

Theory of optical axion electrodynamics and application to the Kerr effect in topological antiferromagnets

Abstract: Emergent axion electrodynamics in magneto-electric media is expected to provide novel ways to detect and control material properties with electromagnetic fields. However, despite being studied intensively for over a decade, its theoretical understanding remains mostly confined to the static limit. Here, we introduce a theory of axion electrodynamics at general frequencies. We define a proper optical axion magneto-electric coupling through its relation to optical surface Hall conductivity and provide ways to calculate it in lattice systems. By employing our formulas, we show that axion electrodynamics can lead to a significant Kerr effect in thin-film antiferromagnets at wavelengths that are seemingly too long to resolve the spatial modulation of magnetism. We identify the wavelength scale above which the Kerr effect is suppressed. Our theory is particularly relevant to materials like MnBi2Te4, a topological antiferromagnet whose magneto-electric response is shown here to be dominated by the axion contribution even at optical frequencies.

Role of spin-lattice coupling in ultrafast demagnetization and all optical helicity-independent single-shot switching in Gd1−x−yTbyCox alloys

Abstract: All optical switching (AOS) of magnetization exhibits a high potential for ultrafast and energy-efficient memory applications. Many works have been carried out in the area of AOS, including its observation in a wide variety of ferromagnetic or ferrimagnetic materials, and the exploration of the parameters for the achievements of AOS such as the laser fluence and helicity, and duration of laser pulses. A large majority of all optical helicity-independent single-shot switching (AO-HIS) has been observed in Gd-based rare-earth transition-metal ferrimagnets. It is then necessary to explore the unique role of Gd in AO-HIS mechanism, compared with other rare-earth elements. Here, we engineered ${\mathrm{Gd}}_{1\ensuremath{-}x\ensuremath{-}y}{\mathrm{Tb}}_{y}{\mathrm{Co}}_{x}$ alloys and investigated the influence of the Tb concentration on the magnetization dynamics via static Kerr microscope and time-resolved magneto-optical Kerr effect (TR-MOKE) measurements. The ultrafast demagnetization time at low fluence is found to be independent of Tb concentration, while both the range of laser fluence and pulse duration allowing for AO-HIS becomes narrower with increasing the Tb concentration. The TR-MOKE signal $\mathrm{\ensuremath{\Delta}}{\mathrm{\ensuremath{\Theta}}}_{K}/{\mathrm{\ensuremath{\Theta}}}_{K_\mathrm{sat}}\ensuremath{\sim}10\phantom{\rule{0.16em}{0ex}}\mathrm{ps}$ after the laser pulse excitation decreases with increasing either the Tb concentration or the pulse duration. The fact that AO-HIS is prohibited by increasing the Tb content is explained by considering a larger damping for Tb than Gd in atomistic simulations. Our results are well explained by the fact that angular momentum can be transferred from Gd to Co resulting in the magnetization switching, whereas for Tb it is dissipated through the lattice due to the large spin-orbit coupling, instead of being transferred between Tb and Co.

Time-reversal symmetry breaking in charge density wave of CsV3Sb5 detected by polar Kerr effect

Abstract: Abstract The Kagome lattice exhibits rich quantum phenomena owing to its unique geometric properties. Appealing realizations are the Kagome metals AV 3 Sb 5 (A = K, Rb, Cs), where unconventional charge density wave (CDW) is intertwined with superconductivity and non-trivial band topology. Several experiments suggest that this CDW is a rare occurrence of chiral CDW characterized by orbital loop current. However, key evidences of loop current, spontaneous time-reversal symmetry-breaking (TRSB) and the coupling of its order parameter with magnetic field remain elusive. Here, we investigate the CDW in CsV3Sb5 by polar Kerr effect. Under magnetic field, we observed a jump of the Kerr angle at the CDW transition. This jump is magnetic-field switchable and scales with field, indicating magneto-chirality coupling related to non-trivial band topology. At zero field, we found non-zero and field-trainable Kerr angle below T CDW , signaling spontaneous TRSB. Our results provide a crucial step to unveil quantum phenomena in correlated Kagome materials.

A Kerr polarization controller

Abstract: Kerr-effect-induced changes of the polarization state of light are well known in pulsed laser systems. An example is nonlinear polarization rotation, which is critical to the operation of many types of mode-locked lasers. Here, we demonstrate that the Kerr effect in a high-finesse Fabry-Pérot resonator can be utilized to control the polarization of a continuous wave laser. It is shown that a linearly-polarized input field is converted into a left- or right-circularly-polarized field, controlled via the optical power. The observations are explained by Kerr-nonlinearity induced symmetry breaking, which splits the resonance frequencies of degenerate modes with opposite polarization handedness in an otherwise symmetric resonator. The all-optical polarization control is demonstrated at threshold powers down to 7 mW. The physical principle of such Kerr effect-based polarization controllers is generic to high-Q Kerr-nonlinear resonators and could also be implemented in photonic integrated circuits. Beyond polarization control, the spontaneous symmetry breaking of polarization states could be used for polarization filters or highly sensitive polarization sensors when operating close to the symmetry-breaking point.

All-dielectric magnetophotonic gratings for maximum TMOKE enhancement.

Abstract: All-dielectric nanophotonic devices are promising candidates for future lossless (bio)sensing and telecommunication applications. Active all-dielectric magnetophotonic devices, where the optical properties can be controlled by an externally applied magnetic field, have triggered great research interest. However, magneto-optical (MO) effects are still low for applications. Here, we demonstrate a concept for the enhancement of the transverse MO Kerr effect (TMOKE), with amplitudes of up to 1.85, i.e., close to the maximum theoretical values of ±2 (in transmission). Our concept exploits the lateral leaky Bloch-modes to enhance the TMOKE, under near-zero transmittance conditions. Potential applications in (bio)sensing structures are numerically demonstrated. The effects of optical losses were studied using different combinations of materials. Significantly, we demonstrate TMOKE enhancements of two orders of magnitude in relation to recent experimental studies, using the same building materials.

Effect of Kerr nonlinearity on signal and pump intensities in EDFA comprising single-mode step index fiber: Estimation by a simple but accurate mathematical formalism

Abstract: The paper presents simple but accurate analytical expressions for the estimation of variation of signal and pump intensity with normalised radial distance in case of erbium doped fiber amplifier. Choosing two typical single-mode step index fibers in our investigation, we hereby predict the said variations relating to both pump and signal in presence as well as absence of Kerr nonlinearity. The stated formulation uses power series expression for the fundamental modal field of graded index optical fiber as derived by Chebyshev formalism. Method of iteration is applied for the prediction of concerned parameters in presence of Kerr type nonlinearity. Our results have been shown to be agreeing excellently with the numerical exact ones in absence and also in presence of Kerr nonlinearity. Exact results in case of Kerr nonlinearity are determined using the cumbersome finite element method. It is noteworthy that execution of our proposed method requires very less computation and as such it will be remarkably user friendly for researchers and technologists associated with nonlinear optical engineering.

Longitudinal Magneto-Optical Kerr Effect of Nanoporous CoFeB and W/CoFeB/W Thin Films

Abstract: Nanoporous Co40Fe40B20 (CoFeB) and sandwich tungsten (W)/CoFeB/W thin films were fabricated via an anodic aluminum oxide (AAO) template-assisted magneto sputtering process. Their thickness-dependent magneto-optical Kerr effect (MOKE) hysteresis loops were investigated for enhanced Kerr rotation. Control of the Kerr null points of the polarized reflected light can be realized via the thicknesses of the CoFeB layers and W layers. Simulation of the thickness-dependent phase difference change by the finite element method reveals the existence of the two Kerr null points for W/CoFeB/W thin films, matching the experimental result very well. However, there are two additional Kerr null points for pure CoFeB thin films according to the simulation by comparing with the experimental result (only one). Theoretical analysis indicates that the different Kerr null points between the experimental result and the simulation are mainly due to the enhanced inner magnetization in the ferromagnetic CoFeB layer with the increased thickness, which is usually omitted in the simulation. Clearly, the introduction of non-ferromagnetic W layers can experimentally regulate the Kerr null points of ferromagnetic thin films. Moreover, construction of W/CoFeB/W sandwich thin films can greatly increase the highest magneto-optical susceptibility and the saturated Kerr rotation angle when compared with CoFeB thin films of the same thickness.

Breathing dynamics of symmetry-broken temporal cavity solitons in Kerr ring resonators.

Abstract: We investigate theoretically and experimentally the instabilities of symmetry-broken, vectorial, bright cavity solitons (CSs) of two-mode nonlinear passive Kerr resonators. Through comprehensive theoretical analyses of coupled Lugiato-Lefever equations, we identify two different breathing regimes where the two components of the vectorial CSs breathe respectively in-phase and out-of-phase. Moreover, we find that deep out-of-phase breathing can lead to intermittent self-switching of the two components, spontaneously transforming a soliton into its mirror-symmetric state. In this process, solitons are also sometimes observed to decay. All our theoretical predictions are confirmed in experiments performed in an optical fiber ring resonator, where CS symmetry breaking occurs across the polarization modes of the resonator. To the best of our knowledge, our study constitutes the first experimental report of breathing instabilities of multi-component optical solitons of driven nonlinear resonators.

Experimental confirmation of the delayed Ni demagnetization in FeNi alloy

Abstract: Element-selective techniques are central for the understanding of ultrafast spin dynamics in multi-element materials like magnetic alloys. Recently, though, it turned out that the commonly used technique of transverse magneto-optical Kerr effect (T-MOKE) in the EUV range may have linearity issues including unwanted cross talk between different elemental signals. This problem can be sizeable, which puts recent observations of ultrafast spin transfer from Fe to Ni sites in FeNi alloys into question. In this study, we investigate the Fe-to-Ni spin transfer in a cross-talk-free time-resolved X-ray magnetic circular dichroism (XMCD) experiment with a reliable time reference. We find a very similar Fe and Ni dynamics with XMCD as with T-MOKE from identical samples. Considering the non-linearities of the T-MOKE response, the agreement with our findings appears fortuitous. We discuss possible reasons why T-MOKE seems to give accurate results in this case. Our data provide the ongoing discussion about ultrafast spin-transfer mechanisms in FeNi systems with a sound experimental basis.

Coherent Combining for High-Power Kerr Combs

Abstract: We demonstrate coherent combining of two Kerr combs operating in the normal group-velocity dispersion regime via on-chip synchronization. We achieve a nearly 2´ increase in the combined comb power while maintaining 26% conversion efficiency.

Vibrational Kerr Solitons in an Optomechanical Microresonator

Abstract: Kerr soliton microcombs in microresonators have been a prominent miniaturized coherent light source. Here, for the first time, we demonstrate the existence of Kerr solitons in an optomechanical microresonator, for which a nonlinear model is built by incorporating a single mechanical mode and multiple optical modes. Interestingly, an exotic vibrational Kerr soliton state is found, which is modulated by a self-sustained mechanical oscillation. Besides, the soliton provides extra mechanical gain through the optical spring effect, and results in phonon lasing with a red-detuned pump. Various nonlinear dynamics is also observed, including limit cycle, higher periodicity, and transient chaos. This work provides a guidance for not only exploring many-body nonlinear interactions, but also promoting precision measurements by featuring superiority of both frequency combs and optomechanics.

Two-color second-order sideband generation via magnon Kerr nonlinearity in a cavity magnonical system

Abstract: We investigate the enhanced generation of the optical second-order sideband (OSS) via magnon Kerr nonlinearity from a cavity magnonical hybrid system consisting of a single small yttrium iron garnet (YIG) crystal sphere and a three-dimensional (3D) rectangular cavity driven with a weak probe and a strong control field. Beyond the linear approximation, we solve the nonlinear Heisenberg–Langevin equations for achieving the analytical solutions by employing the perturbation technique. Using the experimentally achievable parameter settings, we demonstrate that the OSS generation can be significantly enhanced via increasing the magnon Kerr nonlinearity even if the coupling between the cavity and magnon is weak. Interestingly, two-color OSS generation can be observed when the cavity-magnon coupling is in the strong-coupling regime, which results from the magnonical polaritons induced by the hybrid of cavity and magnon modes. The present results illustrate the potential to utilize magnon Kerr nonlinearity for enhancing optical higher-order sidebands and controlling optical frequency combs, as well as to guide the design of experimental implementation.

Electrically controlled optical nonlinear effects in the hybrid opto-electromechanical system with the cross-Kerr effect

Abstract: We theoretically study the nonlinear optical phenomena including optical stability state and four-wave mixing (FWM) process in a hybrid opto-electromechanical system with the cross-Kerr (CK) effect. The hybrid system consists of an optomechanical cavity in which the cross-Kerr (CK) effect and Coulomb interaction are simultaneously introduced by the CK medium and the mechanical resonator capacitively coupling to an external circuit, respectively. The CK interaction induces a tristability behavior of the mean intracavity photon number, which can be modulated by the strength of the CK effect and electrically controlled by the voltage on the capacitor. In addition, we give the effects of the optomechanical, CK, and Coulomb coupling strengths on the FWM of the output field. The results show that the voltage can be employed to electrically engineer the optical nonlinear phenomena.

Steady-entangled-state generation via the cross-Kerr effect in a ferrimagnetic crystal

Abstract: For solid-state spin systems, the collective spin motion in a single crystal embodies multiple magnetostatic modes. Recently, it was found that the cross-Kerr interaction between the higher-order magnetostatic mode and the Kittel mode introduces a new operable degree of freedom. In this work, we propose a scheme to entangle two magnon modes via the cross-Kerr nonlinearity when the bias field is inhomogeneous and the system is driven. Quantum entanglement persists at the steady state, as demonstrated by numerical results using experimentally feasible parameters. Furthermore, we also demonstrate that entangled states can survive better in the system where self-Kerr and cross-Kerr nonlinearities coexist. Our work provides insights and guidance for designing experiments to observe entanglement between different degrees of freedom within a single ferrimagnetic crystal. Additionally, it may stimulate potential applications in quantum information processing using spintronic devices.

Ultrafast element- and depth-resolved magnetization dynamics probed by transverse magneto-optical Kerr effect spectroscopy in the soft x-ray range

Abstract: The authors study element- and depth-resolved ultrafast magnetization dynamics in a GdFe heterostructure by linking laser-induced changes in broadband transverse magneto-optical Kerr effect spectra to the formation of transient magnetization profiles.

Demonstration of DC Kerr effect induced high nonlinear susceptibility in silicon rich amorphous silicon carbide

Abstract: In this study, we demonstrate the DC Kerr effect in plasma-enhanced chemical vapor deposition silicon rich amorphous silicon carbide (a-SiC). Using the resonance shift of the transmission spectra of a ring resonator, we experimentally extract the third order nonlinear susceptibility χ3 to be 6.90×10−19 m2/V2, which is estimated to be more than six times higher than previous reported values in stoichiometric a-SiC. The corresponding induced second order nonlinear susceptibility χ2 of 44.9 pm/V is also three times higher than the reported value in silicon and silicon rich nitride utilizing the DC Kerr effect. The high nonlinearity makes silicon rich a-SiC a good materials candidate for nonlinear photonic applications.