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Two-dimensional layered materials (2DLM) have become the subject of intensive research in various applications such as electronics, photonics and optoelectronics due to their unique physical properties. As a new class of 2DLM, MXenes have attracted great interest due to their superior performance in a wide variety of applications such as batteries, supercapacitors, catalysts, electronics and optics. Here, we have investigated the broadband spatial self-phase modulation (SSPM) and ultrafast response of the MXene Ti (T=O, OH or F) experimentally. The MXene Ti exhibited the broadband nonlinear optical response via SSPM from 400 nm to ~1 μm under the ultrafast laser excitation, and ultrafast carrier characteristics with an ultrafast recovery time with femtosecond transient absorption spectroscopy. The experimental results have shown that the MXenes have the broadband nonlinear optical response, which can lay a foundation for the application prospect for the MXene-based ultrafast optoelectronic devices.

Bismuth sulfide (Bi ) is a binary chalcogenide semiconductor compound that has received much attention in optoelectronic devices because of its stratified structure. In this work we showed that the two-dimensional (2D) Bi shows strong nonlinearity using spatial self-phase modulation and that the all-optical photonic devices, e.g. the all-optical switches and all-optical diodes, have been demonstrated experimentally by observing the nonlinear behavior of the diffraction rings. In addition, an all-optical diode is designed in this work using combined structure with 2D Bi /SnS nanosheet by taking advantage of the reverse saturated absorption of 2D SnS and saturated absorption of 2D Bi . Nonreciprocal light propagation has been achieved with different incident wavelength and a variety of incident intensities. Those characteristics make 2D Bi a potential candidate for the next generation nonreciprocal all-optical device.

Two-dimensional iron phosphorus trichalcogenide (FePS ) has attracted significant attention for its use in electricity, magnetism and optical fields due to its outstanding physical and chemical properties. Herein, FePS was prepared using the chemical vapor transportation (CVT) method and then exfoliated by using fast electrochemical exfoliation. After gradient centrifugation, FePS nanosheets with thicknesses ranging from 1.5 to 20 nm and lateral dimensions of 0.5–3 μm were obtained. By utilizing the spatial self-phase modulation (SSPM) effect, the relationships between the nonlinear refractive index and the size of the FePS nanosheets were investigated in detail which revealed that the nonlinear refractive index can be effectively controlled by the size of the FePS nanosheets. It is worth noting that the optimal FePS nanosheets (3–5 layers thick and ∼1 μm in lateral dimensions) displayed the highest nonlinear refractive index of ∼10  cm  W . This work demonstrates the potential that FePS nanosheets have for use in nonlinear optics or nonlinear optical devices.

Van der Waals heterostructures are composed of stacked atomically thin two-dimensional (2D) crystals to provide unprecedented functionalities and novel physics. Franckeite, a naturally occurring van der Waals heterostructure consisting of superimposed SnS -like and PbS-like layers alternately, shows intriguing potential in versatile optoelectronic applications. Here, we have prepared the few-layer franckeite via liquid-phase exfoliation method and characterized its third-order nonlinearity and ultrafast dynamics experimentally. We have found that the layered franckeite shows low saturable intensity, large modulation depth and picosecond ultrafast response. We have designed the passive photonic diodes based on the layered franckeite/C cascaded film and suspension configuration and found that the passive photonic diodes exhibit stable nonreciprocal transmission of light. The experimental results show the excellent nonlinear optical performance and ultrafast response of the layered franckeite, which may make inroad for the cost effective and reliable high-performance optoelectronic devices.

Plasma channel generation (or filamentation) using ultraintense laser pulses in dielectric media has a wide spectrum of applications, ranging from remote sensing to terahertz generation to lightning control. So far, laser filamentation has been triggered with the use of ultrafast pulses with axially symmetric spatial beam profiles, thereby generating straight filaments. We report the experimental observation of curved plasma channels generated in air using femtosecond Airy beams. In this unusual propagation regime, the tightly confined main intensity feature of the axially nonsymmetric laser beam propagates along a bent trajectory, leaving a curved plasma channel behind. Secondary channels bifurcate from the primary bent channel at several locations along the beam path. The broadband radiation emanating from different longitudinal sections of the curved filament propagates along angularly resolved trajectories.

Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. In a multidomain system this signifies nonlocal coherence and emergence of collective phenomena, particularly in layered 2D quantum materials possessing novel electronic structures and high carrier mobilities. Here we report nonlocal ac electron coherence induced in dispersed MoS₂ flake domains, using coherent spatial self-phase modulation (SSPM). The gap-dependent nonlinear dielectric susceptibilityχ (3)measured is surprisingly large, where direct interband transition and two-photon SSPM are responsible for excitations above and below the bandgap, respectively. A wind-chime model is proposed to account for the emergence of the ac electron coherence. Furthermore, all-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials.

From night vision and objects overwhelmed by sunlight to jammed signals and those that are purposely encrypted, detecting low-level or hidden signals is a fundamental problem in imaging. Here, we develop and exploit a new type of stochastic resonance, in which nonlinear coupling allows signals to grow at the expense of noise, to recover noise-hidden images propagating in a self-focusing medium. The growth rate is derived analytically by treating the signal–noise interaction as a photonic beam–plasma instability and matches experimentally measured resonances in coupling strength, noise statistics and modal content of the signal. This is the first observation of nonlinear intensity exchange between coherent and spatially incoherent light and the first demonstration of spatial coherence resonance for a dynamically evolving signal. The results suggest a general method of reconstructing images through seeded instability and confirm information limits predicted, but not yet observed, in nonlinear communications systems. By exploiting stochastic resonance — in which nonlinear coupling allows signals to grow at the expense of noise — scientists show that they can recover noise-hidden images propagating in a self-focusing medium. The findings pave the way for a variety of nonlinear instability-driven imaging techniques.

It is well known that one cannot image directly through a nonlinear medium, as intensity-dependent phase changes distort signals as they propagate. Indirect methods can be used 1 , 2 , 3 , 4 , 5 , 6 , but none has allowed for the measurement of internal wave mixing and dynamics. Recently, the reconstruction of nonlinear pulse propagation in fibres was demonstrated by generalizing the techniques of digital holography 7 , 8 to the nonlinear domain 9 . The method involves two steps: (1) recording the total field (both amplitude and phase) exiting a nonlinear medium and (2) numerically back-propagating the wavefunction. Here, we extend this process to two-dimensional spatial beams and experimentally demonstrate it in a self-defocusing photorefractive crystal, giving examples in soliton formation, dispersive radiation and imaging. For known nonlinearity, the technique enables reconstruction of wave dynamics within the medium and suggests new methods of super-resolved imaging, including subwavelength microscopy and lithography. For unknown nonlinearity, the method facilitates modelling and characterization of the optical response. Imaging through a nonlinear medium can be difficult because signals distort as they propagate through it owing to intensity-dependent phase changes. Here, digital reconstruction of optical spatial beams propagating in a nonlinear medium is presented, which could help the understanding of coupled-wave dynamics and suggest new image-processing techniques.

In this article, we analytically investigate the spectral broadening by self-phase modulation of strongly chirped optical pulses. The dispersion due to the nonlinear optical process is expressed as functions of a linear and a nonlinear initial chirp. As a result, it is found that the third-order dispersion strongly depends on the initial linear chirp and the nonlinearity for self-phase modulation.

Concatenation model assist in optimising the setup for controlling and manipulating the soliton dynamics. Solitons are self-reinforcing solitary waves that maintain their shape and energy over long distances, also have applications in optics and physics. A thorough analysis of the concatenation model, which incorporates a power law nonlinearity, is presented in this work. This investigation also comprises the phenomena of nonlinear chromatic dispersion, which affects optical fibres and other dispersive media that modulates the chromatic dispersion of the material. When nonlinearities like as self-phase modulation and cross-phase modulation are present, the chromatic dispersion coefficient becomes a function of optical intensity. By employing the modified auxiliary mapping scheme, new families of optical dromions (solions) like bright dromion, domain wall, singular, periodic, doubly periodic, trigonometric, rational and hyperbolic solutions etc. are extracted for the suggested model. The two classes of M -shaped analytical rational solutions are also acquired and by selecting the appropriate values for the relevant parameters, their dynamics are visualised in figures. Likewise two different kinds of interactions between M -shaped rational solutions and kink waves are also computed. In addition, we evaluate periodic cross-rational solutions, kink cross-rational solutions, homoclinic breather solutions and multiwaves solutions for the governing model. The derived solutions have confirmed the potency and stability of the current techniques. In addition, certain solutions graphs are also provided to show the physical nature of the derived results.