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Vladimir L. Kalashnikov

Publications and source records attributed to Vladimir L. Kalashnikov.

At least 19 recordsLinked to original sources

Energy-selective control of noise-assisted multipulsing by weak optical seeding in the dissipative-soliton-resonance regime

We study pulse-number selection in a stochastic cubic--quintic complex Ginzburg--Landau model of a weakly seeded, normal-dispersion laser in the dissipative-soliton-resonance (DSR) regime. Without noise, a single pulse and pulse pairs persist at the same control parameters, and the total energy of an $N$-pulse state follows a ladder constructed from the single-pulse branch. The final energies of noisy trajectories lie close to the same ladder. Multipulsing therefore does not necessarily lose the single-pulse solution. It can reflect which coexisting state the noisy dynamics reaches. Optical seed injection suppresses energy-dependent multipulsing and, at larger seed power, produces a nonmonotonic DSR energy window. An energy--noise scan shows that energy dominates the multipulse probability, whereas additive noise produces only a modest trend common to all energies, without a noise optimum. The noise-induced formation statistics therefore do not establish canonical stochastic resonance or escape from a pre-existing soliton. Coherent control by a weak monochromatic seed extends predominantly single-pulse operation over a noticeably broader energy window, enhancing dissipative-soliton energy scalability. Within an adiabatic approximation, equal energy sharing among coexisting pulses is stable wherever the single-pulse energy grows less than proportionally with the control energy, as it does over the sampled DSR range. Energy exchange between the pulses then relaxes up to about 200 times more slowly than their total energy.

physics.optics↗

Toward a Thermodynamic Framework for Dissipative Solitons: From Photonics to Turbulence and Bose--Einstein Condensate Analogies

# Abstract Thermodynamic concepts are increasingly used in nonlinear photonics to describe Rayleigh--Jeans thermalization, optical wave turbulence, condensation, negative-temperature states, and statistical mode locking. This raises a broader question: how far can thermodynamic reasoning be extended to localized structures maintained far from equilibrium by a balance of gain, loss, dispersion, and nonlinearity? We address this question using strongly chirped dissipative solitons (DSs) of the complex cubic--quintic Ginzburg--Landau equation (CQGLE) as a model system. Their internal energy flows and separation of correlation scales connect coherent solitary waves with semi-incoherent wave kinetics, driven open systems, and Bose--Einstein-condensation analogies. We review thermodynamic-like descriptions based on spectral entropy, internal energy, effective temperature, and condensation-like spectral restructuring, relating them to dissipative-soliton resonance (DSR), stochastic mode-locking self-start, and redistribution between single- and multipulse attractors. Normal and anomalous group-delay dispersion (NGD and AGD) provide complementary realizations: in NGD, DSR is accompanied by spectral localization, scale separation, and increasing accessibility of multipulse states; in AGD, the spectrum has extended wings and dynamical robustness occupies only part of the existence domain. These results distinguish general features of nonequilibrium state selection from effects tied to a particular localization mechanism. We argue that thermodynamic-like observables are best viewed as coarse-grained structural diagnostics rather than equilibrium state variables, while DSs provide a photonic platform linking nonequilibrium thermodynamics, wave turbulence, driven condensates, and statistical phase-transition concepts.

physics.optics↗

Driven Dissipative Soliton Resonance

We investigate the enhancement of the dissipative soliton energy scalability by the injection of a low-power single-mode seed synchronized with a chirped-pulse oscillator round-trip. It is demonstrated that a threshold-like transition to multiple-pulse generation limits the maximum energies of dissipative solitons, in agreement with the thermodynamic interpretation of a strongly chirped pulse stability. We show that there are ``islands'' of instability within a stability range of energies which result from stochastic resonance between ``internal modes'' of soliton and quantum noise of the ``basin''. The transition to multiple-pulsing can be suppressed in a system driven by a comparatively low-power seed. However, seed power growth increases the mode-locking energy threshold and produces ``islands'' of instability as the dissipative soliton energy rises.

physics.optics↗

Energy Scalability Limits of Dissipative Solitons

In this study, we apply a thermodynamical approach to elucidate the primary constraints on the energy scaling of dissipative solitons (DS). We rely on the adiabatic theory of strongly chirped DS and define the DS energy scaling in terms of dissipative soliton resonance (DSR). Three main experimentally verifiable signatures identify a transition to DSR: i) growth of a Lorentzian spike at the centrum of the DS spectrum, which resembles a spectral condensation in Bose-Einstein condensate (BEC), ii) saturation of the spectrum broadening, and iii) asymptotical DS stretching. We connect the DSR breakup with three critical factors: i) decoupling of two correlation scales inherent in strongly chirped DS, ii) resulting rise of the DS entropy with energy, which provokes its disintegration, and iii) transition to a nonequilibrium phase, which is characterized by negative temperature. The breakup results in multiple stable DSs with lower energy. Theoretical results are in good qualitative agreement with the experimental data from a Kerr-lens mode-locked Cr$^{2+}$:ZnS chirped-pulse oscillator (CPO) that paves the way for optimizing high-energy femtosecond pulse generation in solid-state CPO and all-normal-dispersion fiber lasers.

physics.optics↗

Chirped pulse waveguide amplifier

We introduce a single-mode Cr:ZnS crystalline waveguide ultrafast amplifier that provides a high gain of 5.5 dB/cm and 2.35 W of average output power. The depressed-cladding buried waveguide is produced by an ultrafast laser writing procedure, which allows a high degree of flexibility in fabrication when the geometry, size, and even effective index can be modified along the waveguide. An analytical model that includes both, pump and pulse propagation, allows calculation and optimization of the waveguide design. In a CPA arrangement with a volume Bragg grating-based stretcher/compressor, we demonstrate a broadband 34-mm long amplifier in a polycrystalline Cr:ZnS with a single-pass gain factor of 75 (5.5 dB/cm) and a high average output power up to 2.35 W.

physics.optics↗

Dissipative spatiotemporal soliton in a driven waveguide laser

A distributed Kerr-lens mode locking regime can be realized in a waveguide laser by spatial profiling of the pump beam, thus creating a spatio-temporal soliton. Additional slow temporal modulation of the pump source stabilizes the spatio-temporal solution in a broad range of parameters, which are defined by the dynamic gain saturation. We choose a Cr:ZnS waveguide laser as a practical example, but such a regime is feasible in various waveguide and fiber oscillators. A far-reaching analogy with Bose-Einstein condensates allows using this approach to stabilization of the weakly dissipative BECs.

physics.optics↗

Dissipative Soliton Resonance: Adiabatic Theory and Thermodynamics

We present the adiabatic theory of dissipative solitons (DS) of complex cubic-quintic nonlinear Ginzburg-Landau equation (CQGLE). Solutions in the closed analytical form in the spectral domain have the shape of Rayleigh-Jeans distribution for a positive (normal) dispersion. The DS parametric space forms a two-dimensional (or three-dimensional for the complex quintic nonlinearity) master diagram connecting the DS energy and a universal parameter formed by the ratio of four real and imaginary coefficients for dissipative and non-dissipative terms in CQGLE. The concept of dissipative soliton resonance (DSR) is formulated in terms of the master diagram, and the main signatures of transition to DSR are demonstrated and experimentally verified. We show a close analogy between DS and incoherent (semicoherent) solitons with an ensemble of quasi-particles confined by a collective potential. It allows applying the thermodynamical approach to DS and deriving the conditions for the DS energy scalability.

nlin.PS↗

Scalar Product for a Version of Minisuperspace Model with Grassmann Variables

Grassmann variables are used to formally transform a system with constraints into an unconstrained system. As a result, the Schrödinger equation arises instead of the Wheeler-DeWitt one. The Schrödinger equation describes a system's evolution, but a definition of the scalar product is needed to calculate the mean values of the operators. We suggest an explicit formula for the scalar product related to the Klein-Gordon scalar product. The calculation of the mean values is compared with an etalon method in which a redundant degree of freedom is excluded. Nevertheless, we note that a complete correspondence with the etalon picture is not found. Apparently, the picture with Grassmann variables requires a further understanding of the underlying Hilbert space.

gr-qc↗

Rotational Curves of the Milky Way Galaxy and Andromeda Galaxy in Light of Vacuum Polarization around Eicheon

Eicheon properties are discussed. It is shown that the eicheon surface allows setting a boundary condition for the vacuum polarization and obtaining a solution describing the dark matter tail in the Milky Way Galaxy. That is, the dark matter in the Milky Way Galaxy is explained as the F-type of vacuum polarization, which could be treated as dark radiation. The model presented is spherically symmetric, but a surface density of a baryonic galaxy disk is taken into account approximately by smearing the disk over a sphere. This allows the reproduction of the large distance shape of the Milky Way Galaxy rotational curve. Andromeda Galaxy's rotational curve is also discussed.

gr-qc↗

Thermodynamics of Dissipative Solitons

We establish a close analogy between the thermodynamics of the nonlinear systems far from equilibrium and the dissipative solitons. Unlike the solitons in the Hamiltonian systems, their dissipative counterpart looks like an aggregation of bounded quasi-particles interacting on the short range, obeying the Rayleigh-Jeans distribution, and possessing a temperature, entropy, and other thermodynamic characteristics. This ensemble is confined by a collective potential, which defines its negative chemical potential. Such a dissipative soliton represents a strongly chirped pulse generated by a mode-locked laser with the advantage of being energy scalable by the analogy with the Bose-Einstein condensation from an incoherent ``basin.'' We demonstrate the main limits of the dissipative soliton energy scaling which result from the loss of internal soliton coherency and the thermalization due to nontriviality of a ``free energy landscape.''

nlin.PS↗

A route to high peak power and energy scaling in the mid-IR chirped-pulse oscillator-amplifier laser systems

The paper introduces a new route towards the ultrafast high laser peak power and energy scaling in a hybrid mid-IR chirped pulse oscillator-amplifier (CPO-CPA) system, without sacrificing neither the pulse duration nor energy. The method is based on using a CPO as a seed source allowing the beneficial implementation of a dissipative soliton (DS) energy scaling approach, coupled with a universal CPA technique. The key is avoiding a destructive nonlinearity in the final stages of an amplifier and compressor elements by using a chirped high-fidelity pulse from CPO. Our main intention is to realize this approach in a Cr2+:ZnS-based CPO as a source of energy-scalable DSs with well-controllable phase characteristics for a single-pass Cr2+:ZnS amplifier. A qualitative comparison of experimental and theoretical results provides a road map for the development and energy scaling of the hybrid CPO-CPA laser systems, without compromising pulse duration. The suggested technique opens up a route towards extremely intense ultra-short pulses and frequency combs from the multi-pass CPO-CPA laser systems that are particularly interesting for real-life applications in the mid-IR spectral range from 1 to 20 um.

physics.optics↗

AEther as an Inevitable Consequence of Quantum Gravity

The fact that quantum gravity does not admit an invariant vacuum state has far-reaching consequences for all physics. It points out that space could not be empty, and we return to the notion of an aether. Such a concept requires a preferred reference frame for describing universe expansion and black holes. Here, we intend to find a reference system or class of metrics that could be attributed to ``aether''. We discuss a vacuum and quantum gravity from three essential viewpoints: universe expansion, black hole existence, and quantum decoherence.

gr-qc↗

Vacuum polarization instead of "dark matter" in a galaxy

We considered a vacuum polarization inside a galaxy in the eikonal approximation and found that two possible types of polarization exist. The first type is described by the equation of state $p=ρ/3$, similar to radiation. Using the conformally-unimodular metric allows constructing a nonsingular solution for this vacuum ``substance'', if a compact astrophysical object exists in the galaxy's center. As a result, a ``dark'' galactical halo appears that increases the rotation velocity of a test particle as a function of the distance from a galactic center. The second type of vacuum polarization has a more complicated equation of state. As a static physical effect, it produces renormalization of the gravitational constant, thus, causing no static halo. However, a nonstationary polarization of the second type, resulting from an exponential increase (or decrease) of the galactic nuclei mass with time in some hypothetical time-dependent process, produces a gravitational potential looking like a dark matter halo.

gr-qc↗

Stabilization of Spatiotemporal Dissipative Solitons in Multimode Fiber Lasers by External Phase Modulation

In this work, we introduce a method for stabilizing spatiotemporal solitons. These solitons correspond to light bullets in multimode optical fiber lasers, energy-scalable waveguide oscillators and amplifiers, localized coherent patterns in Bose-Einstein condensates, etc. We show that a three-dimensional confinement potential, formed by a spatial transverse (radial) parabolic graded refractive index and dissipation profile, combined with quadratic temporal phase modulation, may permit the generation of stable spatiotemporal dissipative solitons. This corresponds to combining phase mode-locking with the distributed Kerr-lens mode-locking. Our study of the soliton characteristics and stability is based on analytical and numerical solutions of the generalized dissipative Gross-Pitaevskii equation. This approach could lead to higher energy (or condensate mass) harvesting in coherent spatio-temporal beam structures formed in multimode fiber lasers, waveguide oscillators, and weakly-dissipative Bose-Einstein condensates.

physics.optics↗

Eicheons instead of Black holes

A new spherically-symmetric solution for a gravitational field is found in the conformally-unimodular metric. It is shown, that the surface of the black hole horizon in the standard Schwarzschild metric can be squeezed to a point by converting coordinates to the conformally-unimodular metric. In this new metric, there is no black hole horizon, while the naked singularity corresponds to a point massive particle. The reason for the study of this particular gauge (i.e., conformally-unimodular metric) is its relation to the vacuum energy problem. That aims to relate it to other physical phenomena (including black holes), and one could argue that they should be considered in this particular metric. That means the violation of the gauge invariance of the general theory of relativity. As a result, the nonsingular "eicheons" appear as the non-point compact objects with different masses and structures. They are a final product of the stellar collapse, with the masses exceeding the Tolman-Oppenheimer-Volkoff limit.

gr-qc↗

Distributed Kerr-Lens Mode-Locking Based on Spatiotemporal Dissipative Solitons in Multimode Fiber Lasers

We introduce a mechanism of stable spatiotemporal soliton formation in a multimode fiber laser. This is based on spatially graded dissipation, leading to distributed Kerr-lens mode-locking. Our analysis involves solutions of a generalized dissipative Gross-Pitaevskii equation. This equation has a broad range of applications in nonlinear physics, including nonlinear optics, spatiotemporal patterns formation, plasma dynamics, and Bose-Einstein condensates. We demonstrate that careful control of dissipative and non-dissipative physical mechanisms results in the self-emergence of stable (2+1)-dimensional dissipative solitons. Achieving such a regime does not require the presence of any additional dissipative nonlinearities, such a mode-locker in a laser, or inelastic scattering in a Bose-Einstein condensate. Our method allows for stable energy (or "mass") harvesting by coherent localized structures, such as ultrashort laser pulses or Bose-Einstein condensates.

physics.optics↗

Illusiveness of the problem of time

The essay is devoted to the problem of time in the context of quantum cosmology, which acquires a philosophical level to date. At an example of the minisuperspace model, we show that this problem is illusive in the sense that it does not prevent to calculate mean values of the operators over the quantum state of the universe. Contrariwise, the different approaches to the description of these time-dependent mean values give similar results.

gr-qc↗

A phase-space approach to non-stationary nonlinear systems

A phase-space formulation of non-stationary nonlinear dynamics including both Hamiltonian (e.g., quantum-cosmological) and dissipative (e.g., dissipative laser) systems reveals an unexpected affinity between seemly different branches of physics such as nonlinear dynamics far from equilibrium, statistical mechanics, thermodynamics, and quantum physics. One of the key insights is a clear distinction between the "vacuum" and "squeezed" states of a non-stationary system. For a dissipative system, the "squeezed state" (or the coherent "concentrate") mimics vacuum one and can be very attractable in praxis, in particular, for energy harvesting at the ultrashort time scales in a laser or "material laser" physics including quantum computing. The promising advantage of the phase-space formulation of the dissipative soliton dynamics is the possibility of direct calculation of statistical (including quantum) properties of coherent, partially-coherent, and non-coherent dissipative structure without numerically consuming statistic harvesting.

nlin.PS↗