arXiv subjects

Joachim Herrmann

Publications and source records attributed to Joachim Herrmann.

16 recordsLinked to original sources

arXiv2024

Self-compression of 5-$\mu$m pulses in hollow waveguides

We experimentally and numerically investigate self-compression of pulses around 5 $\mu$m wavelength in a noble-gas-filled hollow waveguides. We demonstrate spectral broadening of multi-mJ pulses at 4.9 $\mu$m and associated pulse compression from 85 fs to 47 fs in the solitonic pulse compression regime. The self-compression resulted in sub-three-cycle pulses with 17 GW peak power in the 1-kHz pulse train. A numerical model is established and benchmarked against the experimental results. It allows further insights into the pulse compression process, such as scaling of the compression as a function of gas pressure and waveguide radius, and predicts pulse compression in sub-cycle regime for realistic input parameters.

physics.optics↗

arXiv2023

Ionization-induced Susceptibility by Nearly-free Electrons in Gases Influenced by the Coulomb Potential

In the present paper we study the influence of the Coulomb potential on the real and imaginary parts of the plasma-induced susceptibility in a photoionized gas. We show that the real part of the susceptibility is more than one order of magnitude larger due to the action of a Coulomb potential. Surprisingly, the long-range Coulomb potential of the atomic core leads to an additional contribution to the imaginary part of the susceptibility which has no counterpart in the case of a short-range potential. We demonstrate that the origin of this behavior are electrons in states very close to the continuum (nearly-free electrons), and analyze the dependence of the susceptibility on the intensity and wavelengths.

physics.optics↗

arXiv2022

Towards a unified theory of the fundamental physical interactions based on the underlying geometric structure of the tangent bundle

This paper pursues the hypothesis that the tangent bundle (TB) with the central extended little groups of the SO(3,1) group as gauge group is the underlying geometric structure for a unified theory of the fundamental physical interactions. Based on this hypothesis as a first step recently I presented a generalized theory of electroweak interaction which includes hypothetical dark matter particles (Eur. Phys. J C 79, 779 (2019). The vertical Laplacian of the tangent bundle possesses the same form as the Hamiltonian of a 2D semiconductor quantum Hall system. This explains fractional charge quantization of quarks and the existence of lepton and quark families. As will be shown the SU(3) colour symmetry for strong interaction arises in the TB as an emergent symmetry similar as Chern-Simon gauge symmetries in quantum Hall systems. This predicts a signature of quark confinement as an universal large-scale property of the Chern-Simon fields and induces a new understanding of the vacuum as the ground state occupied with a condensate of quark-antiquark pairs. The gap for quark-antiquark pairing is calculated in the mean-field approximation which allows a numerical estimation of the characteristic parameters of the vacuum such as its chemical potential, the quark condensation parameter and the vacuum energy. Note that previously a gauge theoretical understanding of gravity has been achieved by considering the translation group T(3,1) in the TB as gauge group. Therefore the theory presented here can be considered as a new type of unified theory for all known fundamental interactions linked with the geometrization program of physics.

hep-th↗

arXiv2021

Metallic nanostructures as electronic billiards for nonlinear terahertz photonics

Optical properties of metallic nanoparticles are most often considered in terms of plasmons, the coupled states of light and quasi-free electrons. Here we predict that confinement of electrons inside the nanostructure leads to another, very different, type of resonance, which determines the optical properties in the frequency range significantly below the plasmonic resonance. We demonstrate that closely placed confinement-induces resonances typically join into a single composite "super-resonance" which produces giant nonlinearity at low frequencies. Our simulations show how such nonlinearities can be used for efficient down-conversion of optical pump to terahertz and mid-infrared frequencies in sub-micrometer devices based on nanoparticle composites. We discuss the interaction of these quantum-confinement-induced resonances with the conventional plasmonic ones, as well as the unusual quantum level statistics, adapting here the paradigms of the electronic billiard theory.

physics.optics↗

arXiv2019

Electroweak interaction beyond the Standard Model and Dark Matter in the Tangent Bundle Quantum Field Theory

A generalized theory of electroweak interaction is developed based on the underlying geometrical structure of the tangent bundle with symmetries arising from transformations of tangent vectors along the fiber axis at a fixed space-time point, leaving the scalar product invariant. Transformations with this property are given by the $SO(3,1)$ group with the little groups $SU(2),E^{c}(2)$ and $SU(1,1)$ where the group $E^{c}(2)$ is the central extended group of the Euclidian group $E(2).$ Electroweak interaction beyond the standard model (SM) is described by the transformation group $SU(2)\otimes E^{c}\mathbf{(}2)$ without a priori introduction of a phenomenologically determined gauge group. The Laplacian on this group yields the known internal quantum numbers of isospin and hypercharge, but in addition the extra $E^{c}$-charge $\varkappa $ and the family quantum number $n$ which explains the existence of families in the SM. The connection coefficients deliver the SM gauge potentials but also hypothetical gauge bosons and other hypothetical particles as well as candidate Dark Matter particles are predicted. It is shown that the interpretation of the $SO(3,1)$ connection coefficients as elctroweak gauge potentials is compatible with teleparallel gauge gravity theory based on the translational group.

hep-ph↗

arXiv2018

Ultracompact high-contrast magneto-optical disk resonator side-coupled to a plasmonic waveguide and switchable by an external magnetic field

Here we propose and study a novel type of plasmonic resonators based on a metal-insulator-metal waveguide and a side-coupled magneto-optical disk controlled by an external magnetic field. The wavenumber change and the transmission of surface-plasmon-polaritons (SPPs) can be tuned by altering the magnetic field and reversible on/off switching of the running SPP modes by a reversal of the direction of the external magnetic field is demonstrated. Resonant enhancement of the magneto-plasmonic modulation by more than 200 times leads to a modulation contrast ratio more than tenfold ratio (90-\%-modulation) keeping a moderate insertion loss within an optical bandwidth of hundreds of GHz. Numerical simulations confirm the predictions by the derived analytical formulas of a high-contrast magneto-plasmonic modulation by the submicron ultra-small disk resonator.

physics.optics↗

arXiv2018

All-optical magnetization switching by two-frequency pulses using the plasmon-induced inverse Faraday effect in a magneto-plasmonic structure

In this Letter we study the generation of quasi-static magnetic fields by the plasmon-induced inverse Faraday effect and propose a magneto-optical waveguide structure for achieving magnetization switching at sub-ps time in a nano-confined magneto-optical structure. In particular we show that the direction of the generated quasi-static field in a magneto-optical dielectric cavity side-coupled to a metal-insulator-metal (MIM) waveguide depends sensitively on the wavelength of the surface plasmon polaritions (SPP). This phenomenon could open up a new energy-efficient ultrafast method for nano-confined all-optical magnetization switching by two-frequency pulses.

cond-mat.mes-hall↗

arXiv2018

Switchable plasmonic routers controlled by external magnetic fields by using magneto-plasmonic waveguides

We analytically and numerically investigate magneto-plasmons in metal films surrounded by a ferromagnetic dielectric. In such waveguide using a metal film with a thickness exceeding the Skin depth, an external magnetic field in the transverse direction can induce a significant spatial asymmetry of mode distribution. Superposition of the odd and the even asymmetric modes over a distance leads to a concentration of the energy on one interface which is switched to the other interface by the magnetic field reversal. The requested magnitude of magnetization is exponentially reduced with the increase of the metal film thickness. Based on this phenomenon, we propose a waveguide-integrated magnetically controlled switchable plasmonic routers with 99-%-high contrast within the optical bandwidth of tens of THz. This configuration can also operate as a magneto-plasmonic modulator.

physics.optics↗

arXiv2018

Magnetically-tunable cutoff in asymmetric thin metal film plasmonic waveguide

We theoretically investigated the magnetically-tunable cutoff of long-range surface plasmon polariton along thin metal film surrounded by a magneto-optic material on one side and by a nonmagnetic dielectric on the other side. The analytically derived cutoff condition predicts that a magnetic field bias can induce a novel degenerate cutoff-state near which the beyond-cutoff radiation in one side can be switched to that in the other side by a minor variation of the magnetic field from the bias. The magnetization bias needed for the degeneracy is in proportion to the metal film thickness and in inverse proportion to the wavelength.

physics.optics↗

arXiv2018

Third-order nonlinearity by the inverse Faraday effect in planar magnetoplasmonic structures

We predict a new type of ultrafast third-order nonlinearity of surface plasmon polaritons (SPP) in planar magneto-plasmonic structures caused by the inverse Faraday effect (IFE). Planar SPPs with a significant longitudinal component of the electric field act via the IFE as an effective transverse magnetic field. Its response to the plasmon propagation leads to strong ultrafast self-action which manifests itself through a third-order nonlinearity. We derive a general formula and analytical expressions for the IFE-related nonlinear susceptibility for two specific planar magneto-plasmonic structures from the Lorentz reciprocity theorem. Our estimations predict a very large nonlinear third-order nonlinear susceptibility exceeding those of typical metals such as gold.

physics.optics↗

arXiv2012

All-optical delay of images by backward four-wave mixing in metal-nanoparticle composites

We theoretically study a novel method for all-optical delay of images based on backward four-wave mixing in composites containing metal nanoparticles. In this approach a delayed phase conjugate probe pulse is generated by the interaction of two counter-propagating pump beams and a non-collinear shaped probe pulse in the nanocomposite.The fractional delay and the reflectivity for the phase-conjugate signal pulses are studied as function of the input pump intensity. It is shown that this scheme can be used for delayed imaging combined with the elimination of optical diffraction. The advantages of this method include minituarized design, tunable wavelength range up to the telecommunication range and wide bandwidth.

physics.optics↗

arXiv2012

Slow light in dielectric composite materials of metal nanoparticles

We propose a method for slowing down light pulses by using composites doped with metal nanoparticles. The underlying mechanism is related to the saturable absorption near the plasmon resonance in a pump-probe regime, leading to strong dispersion of the probe refractive index and significantly reduced group velocities. By using the non-collinear scheme, it is possible to realize the total fractional delay of 43 or larger values. This scheme promises simple and compact slow-light on-chip devices with tunable delay and THz bandwidth.

physics.optics↗

arXiv2011

Directionality of THz emission from photoinduced gas plasmas

Forward and backward THz emission by ionizing two-color laser pulses in gas is investigated by means of a simple semi-analytical model based on Jefimenko's equation and rigorous Maxwell simulations in one and two dimensions. We find the emission in backward direction having a much smaller spectral bandwidth than in forward direction and explain this by interference effects. Forward THz radiation is generated predominantly at the ionization front and thus almost not affected by the opacity of the plasma, in excellent agreement with results obtained from a unidirectional pulse propagation model.

physics.optics↗

arXiv2010

Diffusion in the general theory of relativity

The Markovian diffusion theory in the phase space is generalized within the framework of the general theory of relativity. The introduction of moving orthonormal frame vectors both for the position as well the velocity space enables to bypass difficulties in the general relativistic stochastic calculus. The general relativistic Kramers equation in the phase space is derived both in the parametrization of phase space proper time and the coordinate time. The transformation of the obtained diffusion equation under hypersurface-preserving coordinate transformations is analyzed and diffusion in the expanding universe is studied. It is shown that the validity of the fluctuation-dissipation theorem ensures that in the quasi-steady state regime the result of the derived diffusion equation is consistent with the kinetic theory in thermodynamic equilibrium.

gr-qc↗

arXiv2009

High-power Soliton-induced Supercontinuum Generation and Tunable Sub-10-fs VUV Pulses from Kagome-lattice HC-PCFs

We theoretically study a novel approach for soliton-induced high-power supercontinuum generation by using kagome lattice HC-PCFs filled with a noble gas. Anomalous dispersion and broad-band low loss of these fibers enable the generation of two-octave broad spectra by fs pulses, with high coherence and high spectral peak power densities up to five orders of magnitude larger than in standard PCFs. In addition, up to 20 percents of the output radiation energy forms a narrow UV/VUV band, which can be tuned by contolling the pressure in the range from 350 nm to 120 nm. In the temporal domain this corresponds to sub-10-fs UV/VUV pulses with pulse energy of few tens of microjoule, caused by the formation of a high-order soliton emitting non-solitonic radiation.

physics.optics↗

arXiv2009

Diffusion in the special theory of relativity

The Markovian diffusion theory is generalized within the framework of the special theory of relativity using a modification of the mathematical calculus of diffusion on Riemannian manifolds (with definite metric) to describe diffusion on Lorentzian manifolds with an indefinite metric. A generalized Langevin equation in the fiber space of position, velocity and orthonormal velocity frames is defined from which the generalized relativistic Kramers equation in the phase space in external force fields is derived. The obtained diffusion equation is invariant under Lorentz transformations and its stationary solution is given by the Jüttner distribution. Besides a non-stationary analytical solution is derived for the example of force-free relativistic diffusion.

math-ph↗