Optical Rogue Waves Research Articles

Various pulse nonlinear evolution and dynamics employing CuCrO2 nanocrystals as a promising saturable absorber

Considering that fiber lasers are a far richer nonlinear optical system, a systematical study on various pulse nonlinear evolution and dynamics by one SA has great significance. However, investigating these important pulse nonlinear dynamic evolution processes of CuCrO2 nanocrystals as new SAs applied in ultrafast fiber lasers has never been explored. Herein, we demonstrate the excellent nonlinear optical properties of CuCrO2 nanocrystals and investigate the potential of CuCrO2 nanocrystals for generating various pulse nonlinear dynamic evolution processes. Firstly, the output characteristics of the passively Q-switching pulsed fiber lasers have been regulated by using CuCrO2 nanocrystals-polyimide film and a tapered fiber. The pulse duration and repetition rate were simultaneously compressed by 10 and 222 times, the pulse energy and peak power were increased by 79 and 827 times, respectively. Secondly, we are able to generate chaotic multi-pulse wave packets and optical rogue waves by the polarization mode dispersion of single-mode fiber together with the non-instantaneous relaxation of CuCrO2 nanocrystals. Finally, the transition from chaotic multi-pulse wave packet to giant chirped mode-locked pulse is realized by introducing high nonlinear fibers. Our results show that CuCrO2 nanocrystals are an efficient nonlinear material for studying various nonlinear phenomena, and give a new impetus to the development of nonlinear optics and ultrafast photonics.

The poisson property of extreme events in optics

Statistics of extreme events in optics, defined as above-threshold counts of an optical signal, is shown to converge, in the large-sample-size limit, to a generalized Poisson distribution whose mean is found via the exponent of the respective extreme-value distribution. Specifically, extreme-event readouts from polynomial and exponential optical nonlinearities are shown to converge in their statistics to Poisson distributions whose means are, respectively, exponential and slower-than-exponential functions of the extreme-event-counter threshold. Extreme-event counts of a phase readout, on the other hand, converge to a Poisson process whose mean is a light-tailed function of the threshold. The Poisson-limit property of extreme events in optics suggests a powerful resource for a unified treatment of a vast variety of extreme-event phenomena, ranging from optical rogue waves to laser-induced damage.

Generation and control of optical rogue waves by super-Gaussian pulses with varying steepness

We investigate the dynamics of optical rogue waves induced by super-Gaussian (SG) pulses in fiber optics. SG pulses with controlled steep leading and trailing edges can produce high-intensity self-focusing when propagating in nonlinear fibers with weak dispersion and strong nonlinearity. We observe the emergence of various rogue waves, including Peregrine breathers, Akhmediev breathers (ABs), and second-order ABs. By adjusting the steepness of the SG pulses, the generation of these rogue waves can be controlled. As the steepness of the SG pulse increases, we find the fundamental-order AB can stably coexist. Simultaneously, we reveal that the period of these ABs can be effectively controlled by adjusting the steepness of the SG pulse. At a certain steepness, the second-order AB with high power can also be observed. We also investigated the propagation of SG pulses with an initial chirp in fiber optics and found that they can also control AB and second-order Peregrine breathers. To our knowledge, our findings present a new approach to generating controllable rogue waves.

Optical Rogue Waves in Fiber Lasers

Optical Rogue Waves in Fiber Lasers

Deformation of inhomogeneous vector optical rogue waves in the variable coefficients coupled cubic–quintic nonlinear Schrödinger equations with self-steepening

Deformation of inhomogeneous vector optical rogue waves in the variable coefficients coupled cubic–quintic nonlinear Schrödinger equations with self-steepening

Study of Optical Rogue Waves in Two-Dimensional Disordered Lattices

We probed the impact of both the degree of disorder and nonlinearity on rogue waves (RWs) in two-dimensional disordered lattices. Our results unveiled that an increase in the disorder level under linear conditions heightened the probability of RW occurrence and simultaneously contracted the “long tail”. Interestingly, with the introduction of nonlinearity, this “long tail” became shorter compared with linear conditions. Nevertheless, in the context of disordered media, RW occurrence probability demonstrated relative stability—a distinct deviation from its conduct within homogeneous media.

Quantitative analysis of the intensity distribution of optical rogue waves

The field of optical rogue waves is a rapidly expanding topic with a focus on explaining their emergence. To complement this research, instead of providing a microscopic model that generates extreme events, we concentrate on a general quantitative description of the observed behavior. We explore two complementary top-down approaches to estimating the exponent describing the power-law decaying distribution of optical rogue waves observed in supercontinuum generated in a single-mode fiber in the normal-dispersion regime by applying a highly fluctuating pump. The two distinct approaches provide consistent results, outperforming the standard Hill estimator. Further analysis of the distributions reveals the breakdown of power-law behavior due to pump depletion and detector saturation. Either of our methods is adaptable to analyze extreme-intensity events from arbitrary experimental data.

Optical Darboux Transformer.

The optical Darboux transformer for solitons is introduced as a photonic device that performs the Darboux transformation directly in the optical domain. This enables two major advances for optical signal processing based on the nonlinear Fourier transform: (i)the multiplexing of solitonic waveforms corresponding to different discrete eigenvalues of the Zakharov-Shabat system, and (ii)the selective filtering of an arbitrary number of individual solitons too. The optical Darboux transformer can be built using existing commercially available photonic technology components and constitutes a universal tool for signal processing, optical communications, optical rogue waves generation, and waveform shaping and control in the nonlinear Fourier domain.

Unveiling optical rogue wave behavior with temporally localized structures in Brillouin random fiber laser comb

Unveiling optical rogue wave behavior with temporally localized structures in Brillouin random fiber laser comb

Formation of solitons for the modified nonlinear Schrödinger equation

The study of modified nonlinear Schrödinger equation plays a significant role in the description of wave propagation through optical waveguides and rogue waves in ocean. The main aim of this work is to obtain solitons as well as other types of exact wave solutions to the modified nonlinear Schrödinger equation. The accurate traveling wave solutions are obtained using the [Formula: see text]-exponential expansion method and the modified auxiliary equation method. Consequently, soliton solutions and periodic wave solutions have been retrieved. The graphical illustrations of the results are provided for suitable values of the parameters involved in the solutions to explain the dynamical nature of the considered equation.

Numerical investigation on nonautonomous optical rogue waves and Modulation Instability analysis for a nonautonomous system

In this paper, we report existence of optical rogue waves in the focussing non—autonomous nonlinear Schrödinger equation (NLSE) through numerical studies of modulation instability (MI). The dynamics of non-autonomous rogue waves discussed and its associated modulation instability through linear stability analysis taken place followed by pulse splitting behaviour due to non—autonomous coefficient. We prove that the excitation of rogue waves with certain conditions in the base band modulation instability regime. The above analysis of complex dynamics in terms of MI processes has allowed to experiments to excite the nonlinear superposition of rogue wave solutions using a modulated plane wave optical field injected into optical fiber which offer the evidence for excitation of nonautonomous rogue waves in an inhomogeneous nonlinear medium. It is identified from the results frequency modulation on a wavefield induces modulation instability as a result of rogue waves. We analyze the dependence of parameters coefficient of group velocity dispersion(GVD) and nonlinearity (α(z)) and non—autonomous coefficient (β(z)) and the instability of rogue waves. Our work suggests that the presence of non-autonomous coefficients can have a significant impact on the emergence of extreme events, particularly in relation to their self—steepening nature.

Observation of optical rogue waves in 2D optical lattice

Observation of optical rogue waves in 2D optical lattice

Control of Spectral Extreme Events in Ultrafast Fiber Lasers by a Genetic Algorithm

AbstractExtreme wave events or rogue waves (RWs) are both statistically rare and of exceptionally large amplitude. They are observed in many complex systems ranging from oceanic and optical environments to financial models and Bose–Einstein condensates. As they appear from nowhere and disappear without a trace, their emergence is unpredictable and non‐repetitive, which makes them particularly challenging to control. Here, the use of genetic algorithms (GAs), which are exclusively designed for searching and optimizing stationary or repetitive processes in nonlinear optical systems, is extended to the active control of extreme events in a fiber laser cavity. Feeding real‐time spectral measurements into a GA controlling the electronics to optimize the cavity parameters, the wave events are able to be triggered in the cavity that have the typical statistics of RWs in the frequency domain. The intensity of the induced RWs can also be tailored. This accurate control enables the generation of optical RWs with a spectral peak intensity 32.8 times higher than the significant intensity threshold. A rationale is proposed and confirmed by numerical simulations of the laser model for the related frequency up‐ and downshifting of the optical spectrum that are experimentally observed.

Ytterbium-doped fiber laser as a source of coexisting narrow-band thermal light and optical rogue waves: Experimental demonstration

In this paper, we show that a continuous-wave ytterbium-doped fiber laser implemented in the conventional configuration of a Fabry-Perot cavity with two fiber Bragg gratings as selective reflectors and a moderate output power (tens of watts) generates two groups of photons, each of which is characterized by its own statistics. The statistics of the first group are described by the M−fold degenerate Bose-Einstein distribution, where M is the number of independent states of spontaneous emission, which, in turn, depends on the laser linewidth and the radiofrequency band of the recording equipment. This kind of light is classified as narrow-band thermal light. The second group of photons is described by the extreme-value exponential statistics with a probability of encountering extremely large photon events much greater than expected from the Bose-Einstein distribution, which is classified as optical rogue waves. At a low laser power, the first group of photons strongly dominates over the second. As the laser power increases, the fraction of photons of the second group increases monotonically; above a certain threshold, the fraction of this group increases, reaching tens of percent of the total number of laser photons.

Low latency computing for time stretch instruments

Time stretch instruments have been exceptionally successful in discovering single-shot ultrafast phenomena such as optical rogue waves and have led to record-speed microscopy, spectroscopy, lidar, etc. These instruments encode the ultrafast events into the spectrum of a femtosecond pulse and then dilate the time scale of the data using group velocity dispersion. Generating as much as Tbit per second of data, they are ideal partners for deep learning networks which by their inherent complexity, require large datasets for training. However, the inference time scale of neural networks in the millisecond regime is orders of magnitude longer than the data acquisition rate of time stretch instruments. This underscores the need to explore means where some of the lower-level computational tasks can be done while the data is still in the optical domain. The Nonlinear Schrödinger Kernel computing addresses this predicament. It utilizes optical nonlinearities to map the data onto a new domain in which classification accuracy is enhanced, without increasing the data dimensions. One limitation of this technique is the fixed optical transfer function, which prevents training and generalizability. Here we show that the optical kernel can be effectively tuned and trained by utilizing digital phase encoding of the femtosecond laser pulse leading to a reduction of the error rate in data classification.

Enhanced spectral broadening via the optical rogue wave stimulated by spectral sinusoidal phase

We numerically investigate the extended spectral broadening via a spectral sinusoidal phase-modulated Gaussian pulse. The modulated pulse can create two predominant solitons that collide with each other to form a rogue wave (RW), resulting in an RW-induced dispersive wave emission. This leads to a further spectral broadening beyond the soliton-induced dispersive wave and can be manipulated by tuning the phase modulation parameters. Before the appearance of RW, the modulated pulse-propagation scenario is governed by the optical Newton’s cradles and the optical event horizons. These complex dynamics reveal a new method for controlling the RW generation as well as spectral broadening at relatively low power levels. Our results have potential implications for controllable excitation of RWs and broadband supercontinuum generation.

Extreme transport of light in spheroids of tumor cells

Extreme waves are intense and unexpected wavepackets ubiquitous in complex systems. In optics, these rogue waves are promising as robust and noise-resistant beams for probing and manipulating the underlying material. Localizing large optical power is crucial especially in biomedical systems, where, however, extremely intense beams have not yet been observed. We here discover that tumor-cell spheroids manifest optical rogue waves when illuminated by randomly modulated laser beams. The intensity of light transmitted through bio-printed three-dimensional tumor models follows a signature Weibull statistical distribution, where extreme events correspond to spatially-localized optical modes propagating within the cell network. Experiments varying the input beam power and size indicate that the rogue waves have a nonlinear origin. We show that these nonlinear optical filaments form high-transmission channels with enhanced transmission. They deliver large optical power through the tumor spheroid, and can be exploited to achieve a local temperature increase controlled by the input wave shape. Our findings shed light on optical propagation in biological aggregates and demonstrate how nonlinear extreme event formation allows light concentration in deep tissues, paving the way to using rogue waves in biomedical applications, such as light-activated therapies.

Coherence Deterioration in Ultrafast Fiber Lasers Mode-Locked by Nonlinear Polarization Rotation

Ultrafast lasers based on nonlinear polarization rotation has attracted significant attentions, where artificial saturable absorption is induced by Kerr effect. Due to polarization-dependent device within, nonlinear polarization rotation laser cavity generally operates in scalar regime, while vector dynamics have been observed occasionally. However, coherence deterioration induced by nonlinear polarization evolution are rarely reported. Here, we investigate the coherence deterioration for the ultrafast laser systems based on nonlinear polarization rotation. Three types of vector pulses, group velocity locked vector solitons, polarization rotation vector solitons, and coherence deteriorated states can be generated by finely tuning the birefringence of cavity. Combining dispersive Fourier transform and division-of-amplitude facilitates single-shot measurements of wavelength-resolved states of polarization. We find that birefringence-induced phase shift promotes the wavelength-dependent polarization rotation and various polarization evolution speed. In the coherence deteriorated states, optical polarization rogue waves at certain wavelengths are identified, while optical intensities show different irregular probability distributions.

Rogue wave generation using a chaotic semiconductor laser with energy redistribution.

We demonstrate for the first time that optical rogue waves (RWs) can be generated using a chaotic semiconductor laser with energy redistribution. Chaotic dynamics are numerically generated using the rate equation model of an optically injected laser. The chaotic emission is then sent to an energy redistribution module (ERM) that consists of a temporal phase modulation and a dispersive propagation. The process enables a temporal energy redistribution of the chaotic emission waveforms, where coherent summation of consecutive laser pulses leads to random generation of giant intensity pulses. Efficient generation of optical RWs are numerically demonstrated by varying the ERM operating parameters in the entire injection parameter space. The effects of the laser spontaneous emission noise on the generation of RWs are further investigated. The RW generation approach offers a relatively high flexibility and tolerance in the choice of ERM parameters according to the simulation results.

Optical Chaos in Saturated Nonlinear Media

In the study of the evolution of Gaussian beam in saturated nonlinear media, it is found that the probability of optical rogue waves changes with the change of nonlinearity. The light intensity distribution on the exit surface of nonlinear medium can be characterized by scintillation index, and the change of rogue wave corresponds to the evolution of scintillation index. The rogue wave probability shows a complex trend with the evolution of nonlinearity. The Lyapunov exponent and power spectrum method are used to determine that the probability of rogue wave is chaotic with nonlinear evolution.