Achieving optical computing with thousands of tera-operations per second per watt per square millimeter (TOPs/W/mm2) is the key to surpassing electrical computing. This realization requires a breakthrough in the design of a new optical computing architecture and nonlinear activation functions. By leveraging the Kerr effect of silicon and the saturable absorption of graphene, we designed an all-optical nonlinear activator based on a graphene-silicon integrated photonic crystal cavity. The ultralow-threshold, high-speed, compact, and reconfigurable all-optical nonlinear activator could achieve a saturable absorption energy threshold of 4 fJ and a response time of 1.05 ps, a reconfigurable nonlinear activation threshold of 30 fJ and a response time of 4 ps, and an ultrasmall size of 15 μm × 10 μm. This device provides foundation blocks for the picosecond pulsed optical neural network chip to achieve 106 TOPs/W/mm2 level optical computing.

We present an experimental and theoretical study of the interplay between ultrafast electron dynamics and librational dynamics in liquid nitrobenzene. A femtosecond ultraviolet pulse and two femtosecond near-infrared pulses interact with nitrobenzene molecules, generating a four-wave mixing nonlinear signal measured in the Optical Kerr Effect geometry. The signal is measured to be nonzero only at negative time delays, corresponding to the near-infrared pulses arriving before the ultraviolet pulse. We perform time-dependent Quantum Master Equation calculations with classical libration to simulate the experiment. The simulations support the conclusion that the near-infrared pulses launch librational motion while creating electronic coherences resulting in a libration-modulated electronic nonlinear response. The analysis of the phase-matched four-wave mixing signals suggests a nonparametric process leaving the molecules in an excited electronic state, providing new insight into ultrafast nonlinear optical interactions in liquids and advancing toward probing ultrafast electronic coherences in complex molecular liquids.

Universal photon blockade in two coupled cavities with Kerr nonlinearities

Abstract To discover potential altermagnetic materials and decipher their intrinsic properties, we performed high-throughput computational screening on the Materials Project database, with a specific focus on antiferromagnetic compounds belonging to the Pnma space group. This screening identified 140 candidate materials, and further analysis revealed that 91 of these candidates preferentially stabilize in altermagnetic ground states. Taking MnTeO 3 as a prototypical example, we carried out comprehensive first-principles calculations ( GGA+U) and systematic symmetry analysis to explore its electronic structure, magnetic ordering, and orbital configurations. Our results confirm that MnTeO 3 exhibits a G -type antiferromagnetic ( G -AFM) ground state, accompanied by G -type orbital ordering. Notably, the unique symmetry protection inherent to MnTeO 3 ’s G -AFM phase gives rise to distinct altermagnetic responses, including: (i) prominent anomalous transport effects, such as anomalous Hall conductivity (AHC), anomalous Nernst conductivity (ANC), and thermal anomalous Hall conductivity (TAHC); and (ii) strong magneto-optical responses, manifested through pronounced Kerr and Faraday effects.

The magnetic field is one of the most fundamental control parameters in materials science. A pulsed magnetic-field apparatus can generate high magnetic fields that are inaccessible by conventional dc-field magnets. One important issue is that measurement techniques compatible with pulsed fields are rather limited due to short pulse duration and large electromagnetic or mechanical noise originating from field pulses. The magneto-optical Kerr effect (MOKE), the change in the state of light polarization upon reflection from magnetic materials, has the potential to become a powerful tool for investigation of magnetic properties of a wide range of materials including nontransparent materials or thin films in pulsed fields. Nevertheless, since the MOKE response is typically very small, MOKE measurements under pulsed fields are quite challenging. Here, we present a method to measure polar MOKE under high pulsed magnetic fields of 2-ms pulse width. The keys of this technique are a ferrule-based compact sample-fiber fixture and a phase-resolved numerical lock-in analysis, combined with the high-resolution optical apparatus based on an all-fiber loopless Sagnac interferometer. We succeeded in measuring MOKE signals from various ferromagnetic or ferrimagnetic samples above 40 T and down to 77 K, significantly extending the limits of previously reported pulse-field MOKE measurements. Our apparatus is simple enough to be compatible with larger-scale experiments in pulse-field facilities, thus becoming a promising tool to optically investigate material properties in pulsed fields.

In this study, we demonstrate the all-optical control of interfacial spin transport in CoFeB/Ta heterostructures using time-resolved magneto-optical Kerr effect measurements. Our results reveal a reduction in intrinsic Gilbert damping with increasing pump fluence, attributed to the laser-induced thermal modulation of spin diffusion length in Ta. The enhanced spin diffusion length at high pump fluences significantly regulates the spin current transmitted across the interface, leading to a modulation of interfacial spin transparency by up to 85%. These findings demonstrate the potential of ultrafast laser pulses as a noninvasive approach for controlling interfacial spin transport, offering new opportunities for spintronic device optimization.

The process of copper oxidation has been thoroughly studied for many years, yielding a significant understanding of its kinetics and chemistry. However, the possible roles of surface spin polarization in important issues such as oxidation rates have not been widely explored despite the triplet nature of molecular oxygen. Here, we investigate the spin-dependent oxidation of copper films by triplet O2, exploiting engineered ferromagnetic substrates to impose controlled surface spin polarization. Three sample architectures that enable comparison between spin-polarized and nonpolarized surfaces were implemented to enable direct comparison between regions of varying spin polarization on the same sample. Combining various surface-sensitive techniques, including atomic force microscopy, Kelvin probe force microscopy, ellipsometry, and magneto-optical Kerr effect, we followed oxide growth kinetics and electronic property changes over time scales from minutes to weeks. Our results demonstrate that spin-polarized surfaces exhibit a significant acceleration in copper oxide formation compared with less polarized regions. The difference appears to be driven by a preference toward the formation of cupric oxide (CuO), the second oxidation state of copper, over cuprous oxide (Cu2O), the first oxidation state. We suggest that the results are related to the different magnetic properties of each oxide. Our data also reveal that the CuO oxidation phase propagates from the Cu film edges toward the center of the sample. These findings provide direct evidence of the surface-spin influence on metal oxidation kinetics and support the notion that spin polarization can induce a lower activation energy barrier for electron transfer between metal to triplet O2. Beyond advancing the fundamental understanding of corrosion chemistry, this spin-dependent control of surface reactivity opens potential avenues for tailored catalyst design, spintronic device stability, and corrosion mitigation strategies.

Antiferromagnetically coupled ferrimagnets exhibit both ferromagnetic resonance and exchange resonance modes. The antiferromagnetic exchange resonance mode, characterized by a higher magnon frequency than the ferromagnetic resonance mode, holds promise for fast spintronic applications. However, as higher magnon frequencies are typically associated with shorter magnon lifetimes, the exchange resonance mode is expected to decay more rapidly than the ferromagnetic resonance mode, leading to challenges for long-lived information transfer and coherent dynamics. Here we demonstrate that this inverse relationship between frequency and lifetime can be broken in ferrimagnets with two inequivalent magnetic sublattices. Using time-resolved magneto-optical Kerr effect spectroscopy on CoGd, we observe that the exchange resonance mode exhibits a longer magnon lifetime than the ferromagnetic resonance mode near the angular momentum compensation point. Our theoretical and simulation models reveal that this inversion of magnon lifetime arises from the inequivalence in magnetic damping of the two sublattices. The unique combination of higher frequency and longer lifetime in the exchange resonance mode of ferrimagnets highlights its potential for high-speed and energy-efficient spintronic devices.

Nonreciprocal superradiant quantum phase transition induced by the magnon Kerr effect

In this study, we have investigated the concentration-dependent intermolecular dynamics of aqueous solutions of aniline hydrochloride, sodium phenoxide, and 4-methylpyridine using femtosecond Raman-induced Kerr effect spectroscopy at 298 K. The densities, viscosities, and surface tensions of the aqueous solutions were also measured at 298 K. Quantum chemistry calculations of the target aromatics and their clusters with water molecule(s) or a counterion were performed to obtain their optimized structures and cluster interaction energies. In the difference low-frequency Kerr spectra (<250 cm-1) of the aqueous aromatic solutions and neat water, the first moment (M1) of the intermolecular vibrational band, which mainly originated from the aromatic ring, showed that the librations of the anilinium cation and phenoxide anion were higher in frequency than that of 4-methylpydine. Furthermore, the libration of the phenoxide anion was also higher in frequency than that of the anilinium cation. Quantum chemistry calculations indicated that the strong hydrogen bonding and compact hydration structure resulting from the negatively charged aromatic ring led to higher-frequency libration of the phenoxide anion than the anilinium cation. In addition, the M1 increased with increasing concentration. The concentration sensitivities were stronger in aqueous solutions of aniline hydrochloride and sodium phenoxide than in aqueous solutions of 4-methylpyridine. Based on the quantum chemistry calculation results, we conclude that strong aromatic-water and aromatic-counterion interactions lead to a higher-frequency libration of aromatics with charged side groups. The collective orientational relaxation times of the aqueous aromatic solutions showed the fractional Stokes-Einstein-Debye behavior.

Abstract A phase shift keying (PSK) modulator system integrating structured light and Kerr induced effects on TiO 2 -based materials is proposed. TiO 2 and Ag–TiO 2 thin films were prepared by a sol–gel approach and a spin coating deposition method. Morphology and composition analysis confirmed the successful introduction of Ag dopants into the TiO 2 matrix. A remarkable nonlinear refractive index sign change was highlighted from the nonlinear optical characterization by Z-scan experiments on comparable thin films. The induced birefringence generates a fast phase shift in response to high intensity irradiation, which is transformed into a helical wavefront by an optical component, resulting in a very attractive property for precise control over signal modulation for applications in PSK systems. A standard two-wave mixing was implemented to induce Kerr nonlinearities in the studied materials allowing polarization changes and a phase shift. The nonlinearities together with a phase wave plate were employed to generate structured light and an all-optical PSK modulation system. The ability to contrast and tune the phase response in the samples from the Kerr effect results in an interesting research opportunity for direct applications in all-optical telecommunication systems and a variety of nonlinear nanophotonic potential applications.

To address the stringent insulation safety requirements of modern high-voltage transformers, accurately characterizing the transient electric field is critical. However, a significant problem remains: current engineering models typically rely on static capacitive distributions, failing to capture the dynamic electric field distortion induced by rapid space charge injection under lightning impulses. Therefore, a non-contact spatial electric field measurement method based on the optical Kerr effect was employed to analyze the influence of electrode material, voltage amplitude, and wavefront time. Unlike traditional simulation models that often assume constant mobility and focus solely on the shielding effect, this study reveals a non-monotonic electric field evolution driven by a ‘Static-Dynamic’ mode transition. The proposed model highlights two critical breakthroughs: (1) Mechanism Innovation: It experimentally verifies that charge injection is governed by the ion charge-to-mass ratio rather than just the work function, leading to a newly identified field enhancement phase during the wavefront that overcomes the limitations of capacitive models that underestimate transient stress. (2) Parameter Quantification: Precise spatiotemporal thresholds are established—negative charges traverse the gap within ~200 ns, while positive charges require ~10 μs to reach equilibrium. These findings provide experimentally calibrated time constants for simulation correction and offer new criteria for optimizing electrode materials in UHV transformers to mitigate transient field distortion.

On certain novel numerical and analytical solutions for the pure-cubic Schrödinger equation in optical fibers with Kerr nonlinearity.

ABSTRACT On‐chip integration of 2D materials provides a promising route toward next‐generation integrated optical devices with performance beyond existing limits. Here, significantly enhanced spectral broadening induced by self‐phase modulation (SPM) is experimentally demonstrated in silicon nitride (Si 3 N 4 ) waveguides integrated with 2D monolayer molybdenum disulfide (MoS 2 ) films. Monolayer MoS 2 films with ultrahigh optical nonlinearity are synthesized via low‐pressure chemical vapor deposition (LPCVD) and subsequently transferred onto Si 3 N 4 waveguides, with precise control of the film coating length and placement achieved by selectively opening windows on the chip silica upper cladding. Detailed SPM measurements at telecom wavelengths are performed using fabricated waveguides with various MoS 2 film coating lengths. Compared to devices without MoS 2 , increased spectral broadening of sub‐picosecond optical pulses is observed for the hybrid devices, achieving a broadening factor of up to ∼2.4 for a device with a 1.4‐mm‐long MoS 2 film. Theoretical fitting of the experimental results further reveals an increase of up to ∼27 fold in the nonlinear parameter (γ) for the hybrid MoS 2 /Si 3 N 4 waveguides and an equivalent Kerr coefficient ( n 2 ) of MoS 2 nearly 5 orders of magnitude higher than Si 3 N 4 . These results confirm the effectiveness of on‐chip integration of 2D MoS 2 films to enhance the nonlinear optical performance of integrated photonic devices.

It is of great interest to develop methods to rapidly and effectively control the magnetic configurations in artificial spin ices, which are arrangements of dipolar coupled nanomagnets that have a variety of fascinating collective magnetic phenomena associated with them. This is not only valuable in terms of acquiring fundamental understanding but is also important for future high-performance applications. Here, we demonstrate ultrafast control of magnetic relaxation in artificial square ice through femtosecond laser pulsed excitation, enabling rapid access to low-energy states via dipolar interactions. Time-resolved magneto-optical Kerr effect measurements reveal that, after laser-induced demagnetization, the magnetization recovers 60% of its original value within 40 picoseconds. During this brief time window, dipolar coupling drives a collective magnetic ordering. magnetic force microscopy confirms the emergence of extended domains with the lowest-energy vertex configuration, characteristic of ground-state ordering, thus establishing ultrafast laser-driven relaxation as a route to attain the low-energy states. Through complementary energy barrier calculations and micromagnetic simulations incorporating Landau-Lifshitz-Bloch dynamics, we elucidate the underlying mechanism: transient ultrafast demagnetization followed by rapid remagnetization that enables a dipolar-driven collective rearrangement. Moreover, a tailored decreasing-fluence laser excitation protocol is shown to enhance ground-state ordering, consistently achieving over 92% ground-state vertex populations. This work opens the way to ultrafast and spatially selective control of magnetic states in artificial spin ice for spin-based computation and memory technologies, and highlights the critical interplay of thermal fluctuations, magnetostatic coupling, and transient magnetization dynamics.

Abstract In this study, we investigate the generalized stochastic nonlinear Schrödinger equation, which models the propagation of ultrashort optical pulses in nonlinear and dispersive media, incorporating both Kerr effect and higher-order nonlinearities. To construct exact analytical solutions, we employ the tan ( ϖ ( ξ ) 2 ) \tan \left( {{{\varpi (\xi )} \over 2}} \right) -expansion method and the ( G ′/ G , 1/ G )-expansion method. These methods yield a variety of exact solutions, including dark, singular, and singular periodic soliton solutions, each representing different physical wave behaviors. We further perform a stability analysis to determine the robustness of these solutions under perturbations and examine their temporal evolution to better understand their propagation dynamics. Graphical illustrations of selected solutions are provided to visualize their dynamics and to demonstrate how the passage of time influences the structure and stability of the resulting wave forms.

We theoretically study the effects of magnonic Kerr nonlinearity on magnon–polaritons (MPs) with a soft-mode in easy-axis ferromagnets coupled to a microwave cavity. Using an effective circuit model capable of describing MPs up to the nonperturbative strong-coupling regime, we show that chaotic and frequency-comb-like behaviors of MPs emerge at the original modes crossing point. Furthermore, we demonstrate that the Kerr nonlinearity induces a finite excitation gap in the soft-mode, particularly in the strong-coupling regime.

Influence of polarization on Kerr nonlinearity in high-energy laser amplifiers at GW/cm2 level intensities

Abstract Altermagnets have attracted tremendous interest for revealing intriguing physics and promising spintronics applications. In contrast to conventional antiferromagnets, altermagnets break both PT and Tτ symmetries, and simultaneously exhibit spin-split band structures with a vanishing net magnetization. To quantify altermagnetic insulators without conduction electrons, we propose to use the magneto–optical Kerr effect (MOKE). In particular, we demonstrate not only the giant MOKE responses, but also their connection with the orientations of Néel vectors at room temperature in the altermagnetic insulator hematite ( α -Fe 2 O 3 ). Specifically, under the Néel vector along the [ 1 ¯ 100 ] axis, we find a giant polar Kerr rotation angle of 103.7 mdeg in the ( 11 2 ¯ 0 ) plane, which is allowed by the magnetic space group C 2′/ c ′. Under the Néel vector along the [ 11 2 ¯ 0 ] axis, we find a longitudinal Kerr angle of 9.6 mdeg in the (0001) plane, which is allowed by the magnetic space group C 2/ c . Further, we show that such pronounced MOKE effects directly enable optical imaging of altermagnetic domains, together with their reversible domain wall (DW) motion. Our studies not only suggest that MOKE can be used to identify altermagnetic candidates, but also signify the feasibility of exploring altermagnetic optical and DW spintronics, which could largely expand the current research paradigm of altermagnetism.

Laser cutting is an accurate and popular manufacturing process as it is largely employed in most industries in cutting and shaping materials, including electrical steel parts. Nevertheless, laser cutting in the production of motor cores attracts concern regarding its effects to the materials. The resulting localized thermal effects in the cutting can cause mechanical stresses which can also influence the magnetic properties of the electrical steel. In this study, magnetic domains, and their evolution on the magnetic properties of magnets on the surface of non-oriented silicon steel are explored. The magnetization has been carried out at different angles (0°, 30°, 45°, 60°, 90°) to examine local hysteresis properties by magneto-optic Kerr effect methods. Findings indicate that laser cutting causes variations in domain orientations along the cutting edge, more core losses and reduced magnetic susceptibility. Hysteresis loss was observed at the cutting edge 10% higher in the longitudinal direction than loss in the center sample. The loss experienced around the cutting edge in the transverse directions is also 1.5 times the loss experienced at the center, in which case, this means that the energy loss is significantly large. These results indicate that the cutting edge can undergo various changes in microstructural or stress microstructure, as compared to the sheet of the center.