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All-linear time reversal by a dynamic artificial crystal.

Chumak AV, Tiberkevich VS, Karenowska AD, Serga AA, Gregg JF, Slavin AN, Hillebrands B - Nat Commun (2010)

Bottom Line: The time reversal of pulsed signals or propagating wave packets has long been recognized to have profound scientific and technological significance.Until now, all experimentally verified time-reversal mechanisms have been reliant upon nonlinear phenomena such as four-wave mixing.As a result, a linear coupling between wave components with wave vectors k≈π/a and k'=k-2π/a≈-π/a is produced, which leads to spectral inversion, and thus to the formation of a time-reversed wave packet.

View Article: PubMed Central - PubMed

Affiliation: Fachbereich Physik and Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany. chumak@physik.uni-kl.de

ABSTRACT
The time reversal of pulsed signals or propagating wave packets has long been recognized to have profound scientific and technological significance. Until now, all experimentally verified time-reversal mechanisms have been reliant upon nonlinear phenomena such as four-wave mixing. In this paper, we report the experimental realization of all-linear time reversal. The time-reversal mechanism we propose is based on the dynamic control of an artificial crystal structure, and is demonstrated in a spin-wave system using a dynamic magnonic crystal. The crystal is switched from an homogeneous state to one in which its properties vary with spatial period a, while a propagating wave packet is inside. As a result, a linear coupling between wave components with wave vectors k≈π/a and k'=k-2π/a≈-π/a is produced, which leads to spectral inversion, and thus to the formation of a time-reversed wave packet. The reversal mechanism is entirely general and so applicable to artificial crystal systems of any physical nature.

No MeSH data available.


Related in: MedlinePlus

Experimental dynamic magnonic crystal (DMC) system.(a) The DMC comprises a planar current-carrying meander structure with 20 periods of lattice constant a=300 μm (10 shown), positioned close to the surface of an Yttrium Iron Garnet thin-film spin-wave waveguide (thickness 5 μm, width 2 mm). Two spin-wave antennae are arranged on the surface of the film 8 mm apart: one to launch a spin-wave signal, amplitude AS(t) and to detect the signal AR(t) reflected by the DMC, and a second to detect the signal AT(t) transmitted through it. (b) Theoretical spin-wave dispersion relationship for the waveguide with no applied current (dotted, light blue) and with a static current of 1 A in the meander structure (solid curve, dark blue). (c) Experimental spin-wave transmission characteristics with no current (dotted, light blue) and with a current of 1 A (solid curve, dark blue) applied to the meander structure. Application of the current leads to the formation of a bandgap of width approximately Δfa=30 MHz, centred on fa=6,500 MHz.
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f1: Experimental dynamic magnonic crystal (DMC) system.(a) The DMC comprises a planar current-carrying meander structure with 20 periods of lattice constant a=300 μm (10 shown), positioned close to the surface of an Yttrium Iron Garnet thin-film spin-wave waveguide (thickness 5 μm, width 2 mm). Two spin-wave antennae are arranged on the surface of the film 8 mm apart: one to launch a spin-wave signal, amplitude AS(t) and to detect the signal AR(t) reflected by the DMC, and a second to detect the signal AT(t) transmitted through it. (b) Theoretical spin-wave dispersion relationship for the waveguide with no applied current (dotted, light blue) and with a static current of 1 A in the meander structure (solid curve, dark blue). (c) Experimental spin-wave transmission characteristics with no current (dotted, light blue) and with a current of 1 A (solid curve, dark blue) applied to the meander structure. Application of the current leads to the formation of a bandgap of width approximately Δfa=30 MHz, centred on fa=6,500 MHz.

Mentions: We demonstrate our proposed time-reversal mechanism experimentally using spin waves in a dynamic magnonic crystal (DMC)14 (Fig. 1a). The use of spin-wave systems as model environments for the study of general wave and quasi-particle phenomena is well established25262728293031 and, indeed, in this context, magnonic crystals are increasingly recognized as an important route to fundamental understanding of wave dynamics in metamaterials14151617181920. The process of time reversing a signal is equivalent, in the frequency domain, to an inversion of its spectrum about a certain reference frequency2. Accordingly, for clarity, we reveal our time-reversal mechanism through two separate experiments. The first demonstrates frequency inversion of quasi-monochromatic signals and the second demonstrates time reversal of complex waveforms.


All-linear time reversal by a dynamic artificial crystal.

Chumak AV, Tiberkevich VS, Karenowska AD, Serga AA, Gregg JF, Slavin AN, Hillebrands B - Nat Commun (2010)

Experimental dynamic magnonic crystal (DMC) system.(a) The DMC comprises a planar current-carrying meander structure with 20 periods of lattice constant a=300 μm (10 shown), positioned close to the surface of an Yttrium Iron Garnet thin-film spin-wave waveguide (thickness 5 μm, width 2 mm). Two spin-wave antennae are arranged on the surface of the film 8 mm apart: one to launch a spin-wave signal, amplitude AS(t) and to detect the signal AR(t) reflected by the DMC, and a second to detect the signal AT(t) transmitted through it. (b) Theoretical spin-wave dispersion relationship for the waveguide with no applied current (dotted, light blue) and with a static current of 1 A in the meander structure (solid curve, dark blue). (c) Experimental spin-wave transmission characteristics with no current (dotted, light blue) and with a current of 1 A (solid curve, dark blue) applied to the meander structure. Application of the current leads to the formation of a bandgap of width approximately Δfa=30 MHz, centred on fa=6,500 MHz.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3105294&req=5

f1: Experimental dynamic magnonic crystal (DMC) system.(a) The DMC comprises a planar current-carrying meander structure with 20 periods of lattice constant a=300 μm (10 shown), positioned close to the surface of an Yttrium Iron Garnet thin-film spin-wave waveguide (thickness 5 μm, width 2 mm). Two spin-wave antennae are arranged on the surface of the film 8 mm apart: one to launch a spin-wave signal, amplitude AS(t) and to detect the signal AR(t) reflected by the DMC, and a second to detect the signal AT(t) transmitted through it. (b) Theoretical spin-wave dispersion relationship for the waveguide with no applied current (dotted, light blue) and with a static current of 1 A in the meander structure (solid curve, dark blue). (c) Experimental spin-wave transmission characteristics with no current (dotted, light blue) and with a current of 1 A (solid curve, dark blue) applied to the meander structure. Application of the current leads to the formation of a bandgap of width approximately Δfa=30 MHz, centred on fa=6,500 MHz.
Mentions: We demonstrate our proposed time-reversal mechanism experimentally using spin waves in a dynamic magnonic crystal (DMC)14 (Fig. 1a). The use of spin-wave systems as model environments for the study of general wave and quasi-particle phenomena is well established25262728293031 and, indeed, in this context, magnonic crystals are increasingly recognized as an important route to fundamental understanding of wave dynamics in metamaterials14151617181920. The process of time reversing a signal is equivalent, in the frequency domain, to an inversion of its spectrum about a certain reference frequency2. Accordingly, for clarity, we reveal our time-reversal mechanism through two separate experiments. The first demonstrates frequency inversion of quasi-monochromatic signals and the second demonstrates time reversal of complex waveforms.

Bottom Line: The time reversal of pulsed signals or propagating wave packets has long been recognized to have profound scientific and technological significance.Until now, all experimentally verified time-reversal mechanisms have been reliant upon nonlinear phenomena such as four-wave mixing.As a result, a linear coupling between wave components with wave vectors k≈π/a and k'=k-2π/a≈-π/a is produced, which leads to spectral inversion, and thus to the formation of a time-reversed wave packet.

View Article: PubMed Central - PubMed

Affiliation: Fachbereich Physik and Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany. chumak@physik.uni-kl.de

ABSTRACT
The time reversal of pulsed signals or propagating wave packets has long been recognized to have profound scientific and technological significance. Until now, all experimentally verified time-reversal mechanisms have been reliant upon nonlinear phenomena such as four-wave mixing. In this paper, we report the experimental realization of all-linear time reversal. The time-reversal mechanism we propose is based on the dynamic control of an artificial crystal structure, and is demonstrated in a spin-wave system using a dynamic magnonic crystal. The crystal is switched from an homogeneous state to one in which its properties vary with spatial period a, while a propagating wave packet is inside. As a result, a linear coupling between wave components with wave vectors k≈π/a and k'=k-2π/a≈-π/a is produced, which leads to spectral inversion, and thus to the formation of a time-reversed wave packet. The reversal mechanism is entirely general and so applicable to artificial crystal systems of any physical nature.

No MeSH data available.


Related in: MedlinePlus