Optical Shock Waves Research Articles

Shock-wave generation and propagation in dissipative and nonlocal nonlinear Rydberg media

We investigate the generation of optical shock waves in strongly interacting Rydberg atomic gases with a spatially homogeneous dissipative potential. The Rydberg atom interaction induces an optical nonlocal nonlinearity. We focus on local nonlinear (Rb≪R0) and nonlocal nonlinear (Rb∼R0) regimes, where Rb and R0 are the characteristic length of the Rydberg nonlinearity and beam width, respectively. In the local regime, we show spatial width and contrast of the shock wave change monotonically when increasing strength of the dissipative potential and optical intensity. In the nonlocal regime, the characteristic quantity of the shock wave depends on Rb/R0 and dissipative potential nontrivially and on the intensity monotonically. We find that formation of shock waves dominantly takes place when Rb is smaller than R0, while the propagation dynamics is largely linear when Rb is comparable to or larger than R0. Our results reveal nontrivial roles played by dissipation and nonlocality in the generation of shock waves, and provide a route to manipulate their profiles and stability. Our study furthermore opens new avenues to explore non-Hermitian physics and nonlinear wave generation and propagation by controlling dissipation and nonlocality in the Rydberg media. Published by the American Physical Society 2024

Bifurcation Analysis and Bounded Optical Soliton Solutions of the Biswas-Arshed Model

We investigate the bounded travelling wave solutions of the Biswas-Arshed model (BAM) including the low group velocity dispersion and excluding the self-phase modulation. We integrate the nonlinear structure of the model to obtain bounded optical solitons which pass through the optical fibers in the non-Kerr media. The bifurcation technique of the dynamical system is used to achieve the parameter bifurcation sets and split the parameter space into various areas which correspond to different phase portraits. All bounded optical solitons and bounded periodic wave solutions are identified and derived conforming to each region of these phase portraits. We also apply the extended sinh-Gordon equation expansion and the generalized Kudryashov integral schemes to obtain additional bounded optical soliton solutions of the BAM nonlinearity. We present more bounded optical shock waves, the bright-dark solitary wave, and optical rogue waves for the structure model via these schemes in different aspects.

The piston Riemann problem in a photon superfluid

Light flow in nonlinear media can exhibit quantum hydrodynamical features which are profoundly different from those of classical fluids. Here, we show that a rather extreme regime of quantum hydrodynamics can be accessed by exploring the piston problem (a paradigm in gas dynamics) for light, and its generalization, named after the celebrated mathematician Riemann, where the piston acts on a concomitant abrupt change of photon density. Our experiment reveals regimes featuring optical rarefaction (retracting piston) or shock (pushing piston) wave pairs, and most importantly the transition to a peculiar type of flow, occurring above a precise critical piston velocity, where the light shocks are smoothly interconnected by a large contrast, periodic, fully nonlinear wave. The transition to such extreme hydrodynamic state is generic for superfluids, but to date remained elusive to any other quantum fluid system. Our full-fiber setup used to observe this phenomenon in temporal domain proves to be a versatile alternative to other platforms currently employed to investigate the hydrodynamical properties of quantum fluids of light.

Nematic Dispersive Shock Waves from Nonlocal to Local

The structure of optical dispersive shock waves in nematic liquid crystals is investigated as the power of the optical beam is varied, with six regimes identified, which complements previous work pertinent to low power beams only. It is found that the dispersive shock wave structure depends critically on the input beam power. In addition, it is known that nematic dispersive shock waves are resonant and the structure of this resonance is also critically dependent on the beam power. Whitham modulation theory is used to find solutions for the six regimes with the existence intervals for each identified. These dispersive shock wave solutions are compared with full numerical solutions of the nematic equations, and excellent agreement is found.

Quantitative Analysis of Shock Wave Dynamics in a Fluid of Light.

We report on the formation of a dispersive shock wave in a nonlinear optical medium. We monitor the evolution of the shock by tuning the incoming beam power. The experimental observations for the position and intensity of the solitonic edge of the shock, as well as the location of the nonlinear oscillations are well described by recent developments of Whitham modulation theory. Our work constitutes a detailed and accurate benchmark for this approach. It opens exciting possibilities to engineer specific configurations of optical shock wave for studying wave-mean flow interaction.

Anisotropic Optical Shock Waves in Isotropic Media with Giant Nonlocal Nonlinearity.

Dispersive shock waves in thermal optical media are nonlinear phenomena whose intrinsic irreversibility is described by time asymmetric quantum mechanics. Recent studies demonstrated that the nonlocal wave breaking evolves in an exponentially decaying dynamics ruled by the reversed harmonic oscillator, namely, the simplest irreversible quantum system in the rigged Hilbert spaces. The generalization of this theory to more complex scenarios is still an open question. In this work, we use a thermal third-order medium with an unprecedented giant Kerr coefficient, the m-cresol/nylon mixed solution, to access an extremely nonlinear, highly nonlocal regime and realize anisotropic shock waves with internal gaps. We compare our experimental observations to results obtained under similar conditions but in hemoglobin solutions from human red blood cells, and found that the gap formation strongly depends on the nonlinearity strength. We prove that a superposition of Gamow vectors in an adhoc rigged Hilbert space, that is, a tensorial product between the reversed and the standard harmonic oscillators spaces, describes the beam propagation beyond the shock point. The anisotropy turns out from the interaction of trapping and antitrapping potentials. Our work furnishes the description of novel intriguing shock phenomena mediated by extreme nonlinearities.

Sub-half-cycle field transients from shock-wave-assisted soliton self-compression

We identify an unusual regime of ultrafast nonlinear dynamics in which an optical shock wave couples to soliton self-compression, steepening the tail of the pulse, thus yielding self-compressing soliton transients as short as the field sub-half-cycle. We demonstrate that this extreme pulse self-compression scenario can help generate sub-half-cycle mid-infrared pulses in a broad class of anomalously dispersive optical waveguide systems.

Optical soliton solutions of the Biswas-Arshed model by the expansion approach

In this paper, we consider the Biswas-Arshed model (BAM) with nonlinear Kerr and power law. We integrate these nonlinear structures of the BAM to obtain optical exact solitons that passing through the optical fibers. To retrieve the solutions, we apply the expansion integral scheme to the structures of the BAM nonlinearity. The novel solutions present optical shock wave, double periodic optical solitons, interaction between optical periodic wave and optical solitons, and optical periodic and rogue waves for both structures of the model. It is shown that the amplitude of the periodic double solitons waves gradually increases and reached the highest peak at the moment of interaction, and it goes to diminish for a much larger time. In fact, we show that the amplitude of the wave for the interaction between periodic and optical solitons, gradually increases with beat phenomena. To the purpose, all these types of optical solitons can be frequently used to amplify or reduce waves for a certain hight. Moreover, we describe the physical phenomena of the solitons in graphically.

Picosecond-resolution phase-sensitive imaging of transparent objects in a single shot.

With the growing interest in the optical imaging of ultrafast phenomena in transparent objects, from shock wave to neuronal action potentials, high contrast imaging at high frame rates has become desirable. While phase sensitivity provides the contrast, the frame rates and sequence depths are highly limited by the detectors. Here, we present phase-sensitive compressed ultrafast photography (pCUP) for single-shot real-time ultrafast imaging of transparent objects by combining the contrast of dark-field imaging with the speed and the sequence depth of CUP. By imaging the optical Kerr effect and shock wave propagation, we demonstrate that pCUP can image light-speed phase signals in a single shot with up to 350 frames captured at up to 1 trillion frames per second. We expect pCUP to be broadly used for a vast range of fundamental and applied sciences.

Modulation theory and resonant regimes for dispersive shock waves in nematic liquid crystals

A full analysis of all regimes for optical dispersive shock wave (DSW) propagation in nematic liquid crystals is undertaken. These dispersive shock waves are generated from step initial conditions for the optical field and are resonant in that linear diffractive waves are in resonance with the DSW, resulting in a resonant linear wavetrain propagating ahead of it. It is found that there are six regimes, which are distinct and require different solution methods. In previous studies, the same solution method was used for all regimes, which does not yield solutions in full agreement with numerical solutions. Indeed, the standard DSW structure disappears for sufficiently large initial jumps. Asymptotic theory, approximate methods or Whitham modulation theory are used to find solutions for these resonant dispersive shock waves in a given regime. The solutions are found to be in excellent agreement with numerical solutions of the nematic equations in all regimes. It is found that for small initial jumps, the resonant wavetrain is unstable, but that it stabilises above a critical jump height. It is additionally found that the DSW is unstable, except for small jump heights for which there is no resonance and large jump heights for which there is no standard DSW structure.

Optical shock wave and photon-number conservation

The nonlinear Schr\odinger equation (NSE) provides a powerful tool for the analysis of ultrafast nonlinear-optical dynamics, including a vast class of optical solitons. Here, we show, however, that the photon-number integral of the NSE differs from the physical number of photons, conserved by more general field evolution equations. This difficulty is traced to the optical shock term, which is dropped in the NSE, making nonlinear coupling in NSE-based models frequency independent and leading to unphysical predictions for ultrabroadband, octave-spanning field waveforms.

Characteristics of exploding metal wires in water with three discharge types

This paper presents the characteristics of underwater electrical wire explosion (UEWE) with three discharge types, namely, Type-A, Type-B, and Type-C. Experiments were carried out with copper and tungsten wires (4 cm long and 50–300 μm in diameter) driven by a microsecond time-scale pulsed current source with 500 J stored energy. A time-integrated spectrometer and a photodiode were used to measure the optical emission of UEWE. A Polyvinylidene Fluoride probe was adopted to record the pressure waveforms. Experimental results indicate that from Type-A to Type-C, more energy deposits prior to the voltage peak and the first peak power increases drastically. This variation of energy deposition influences the optical emission and shock wave generation process. Specifically, the light intensity decreases by more than 90% and the peak of continuous spectra moves from ∼400 nm to ∼700 nm. In addition, the peak pressure of the first shock wave increases from ∼2 MPa to more than 7.5 MPa.

Spatiotemporal evolution of continuous-wave field and dark soliton formation in a microcavity with normal dispersion**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFF0200702), the National Natural Science Foundation of China (Grant Nos. 61690222 and 11573058), and the CAS-SAFEA International Partnership Program for Creative Research Teams.

Stable dark soliton and dark pulse formation in normally dispersive and red-detuned microcavities are investigated by numerically solving the normalized Lugiato-Lefever equation. The soliton essence is proved by fitting the calculated field intensity profile with the analytical formula of a dark soliton. Meanwhile, we find that a dark soliton can be generated either from the nonlinear evolution of an optical shock wave or narrowing of a locally broad dark pulse with smoother fronts. Explicit analytical expression is obtained to describe the oscillatory fronts of the optical shock wave. Furthermore, from the calculation results, we show that for smaller frequency detunings, e.g., , in addition to the dark soliton formation, a single dark pulse with an oscillatory dip can also arise and propagate stably in the microcavity under proper pump detuning and pump strength combination. The existence region together with various field intensity profiles and the corresponding spectra of single dark pulse are demonstrated.

Optical dispersive shock waves in defocusing colloidal media

The propagation of an optical dispersive shock wave, generated from a jump discontinuity in light intensity, in a defocusing colloidal medium is analysed. The equations governing nonlinear light propagation in a colloidal medium consist of a nonlinear Schrödinger equation for the beam and an algebraic equation for the medium response. In the limit of low light intensity, these equations reduce to a perturbed higher order nonlinear Schrödinger equation. Solutions for the leading and trailing edges of the colloidal dispersive shock wave are found using modulation theory. This is done for both the perturbed nonlinear Schrödinger equation and the full colloid equations for arbitrary light intensity. These results are compared with numerical solutions of the colloid equations.

Subcycle solitonic breathers

Optical breathing solitons are known to display well-resolved cycles where the phase of pulse compression is followed by pulse stretching. Here we show that, in the extreme regimes where the soliton pulse width approaches the field cycle, the field waveform dynamics can drastically differ from this textbook scenario. We demonstrate that such extremely short soliton transients can develop optical shock waves, which seed parametric amplification, facilitating, along with ionization nonlinearity, soliton compression to subcycle pulse widths. This pulse compression scenario is shown to enable the generation of sub-quarter-cycle multigigawatt optical field waveforms in the mid infrared.

Underwater blast wave pressure sensor based on polymer film fiber Fabry-Perot cavity.

This paper describes the theoretical and experimental aspects of an optical underwater shock wave sensor based on a polymer film optical fiber Fabry-Perot cavity manufactured by vacuum deposition technology. The transduction mechanism of the sensor involves a normally incident acoustic stress wave that changes the thickness of the polymer film, thereby giving rise to a phase shift. This transient interferometric phase is interrogated by a three-phase-step algorithm. Theoretically, the sensor-acoustic-field interaction principle is analyzed, and the phase modulation sensitivity based on the theory of waves in the layered media is calculated. Experimentally, a static calibration test and a dynamic calibration test are conducted using a piston-type pressure calibration machine and a focusing-type electromagnetic shock wave. Results indicate that the repeatability, hysteresis, nonlinearity, and the overall measurement accuracy of the sensor within the full pressure range of 55MPa are 1.82%, 0.86%, 1.81%, and 4.49%, respectively. The dynamic response time is less than 0.767μs. Finally, three aspects that need further study for practical use are pointed out.

Optical shock waves in silica aerogel

Silica aerogels are materials well suited for high power nonlinear optical applications. In such regime, the non-trivial thermal properties may give rise to the generation of optical shock waves, which are also affected by the structural disorder due to the porous solid-state gel. Here we report on an experimental investigation in terms of beam waist and input power, and identify various regimes of the generation of wave-breaking phenomena in silica aerogels.

Optical shocks in resonant media: The role of inhomogeneous broadening

We discover and numerically describe optical shock wave formation in inhomogeneously broadened resonant nonlinear media. Our results extend our previous work to the case of inhomogeneously broadened two-level media. We also describe in detail the atomic variable behavior as the optical shocks form in the medium.

Theoretical and experimental investigations of spatial optical dark soliton filamentization in nonlocal self-defocusing Kerr medium

In this paper, the spatial optical dark soliton filamentization in a nonlocal self-defocusing Kerr medium is investigated. Theoretically, starting from nonlocal nonlinear theoretical model, we examine the influences of the degree of nonlocality and the attenuation constant on the formation of dark soliton filaments by numerical simulation method. We find that when the input background optical intensity is determined, the greater the degree of nonlocality, the farther the initial point of the formation of dark filaments is and the less the number of dark filaments decreases with the increase of the degree of nonlocality; when the ratio of the background optical intensity to the critical optical intensity is fixed, the degree of nonlocality can hardly influence the number of dark filaments and the number of dark filaments under nonlocality is equal to that under locality. Besides, when the input background optical intensity is determined, the number of dark filaments decreases with the increase of the attenuation constant. Experimentally, by changing the concentration of dye solution and the ellipticity of background light, we discuss the influences of the concentration of sample and the ellipticity of background light on the formation of dark soliton filaments respectively and find that when the input background average optical intensity is determined, the number of dark filaments decreases with the increases of the concentration of sample and the ellipticity of background light; when the ratio of the background average optical intensity to the critical optical intensity is fixed, the concentration of sample can hardly influence the number of dark filaments. Besides, the phenomenon of optical shock wave is found in our experiment.

On the possibility of suppression of self-focusing of a femtosecond laser pulse during its propagation in a cubic nonlinear medium

Based on a computer simulation, the self-focusing of an axially symmetric beam in a cubic nonlinear medium under the anomalous dispersion conditions is studied with the account for the time dispersion of nonlinear response, which manifests for femtosecond pulses. It is shown that, at a certain value of the parameter of linear modulation of the pulse (or of its chirp), the dispersion of nonlinear response can lead either to the suppression of formation of a nonlinear focus and to the possibility of formation of optical shock waves in time or even to a change in the regime of the beam self-action owing to the action of the local response, i.e., to the change from the self-focusing of the beam to the regime of its defocusing.