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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 demonstration of frequency inversion by the dynamic magnonic crystal.(a) When the carrier frequency of the incident spin-wave signal packet is detuned from the resonance value of 6,500 MHz (the bandgap centre frequency), the frequency of the reflected signal is inverted about this value (left ordinate axis, red diamonds). The solid red line is the theoretical curve of equation (2). The efficiency of the reflection process (right ordinate axis, blue circles) is maximum at the resonance condition and decreases symmetrically with detuning. (b) Two-dimensional map of reflected signal spectra as a function of the incident signal carrier frequency fS (31 spectra taken at 1 MHz intervals of fS). Dark red is indicative of the highest signal intensities, dark blue the lowest; the intervening colour scale is linear. Frequency inversion is clearly demonstrated by the diagonal stripe of high signal intensity with a negative slope (running from the upper left to the lower right corner of the figure). The weak diagonal stripe with a positive slope (from the lower left to the upper right corner) is due to weak conventional (that is, frequency conserving) reflection from inhomogeneities in the spin-wave waveguide.
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f3: Experimental demonstration of frequency inversion by the dynamic magnonic crystal.(a) When the carrier frequency of the incident spin-wave signal packet is detuned from the resonance value of 6,500 MHz (the bandgap centre frequency), the frequency of the reflected signal is inverted about this value (left ordinate axis, red diamonds). The solid red line is the theoretical curve of equation (2). The efficiency of the reflection process (right ordinate axis, blue circles) is maximum at the resonance condition and decreases symmetrically with detuning. (b) Two-dimensional map of reflected signal spectra as a function of the incident signal carrier frequency fS (31 spectra taken at 1 MHz intervals of fS). Dark red is indicative of the highest signal intensities, dark blue the lowest; the intervening colour scale is linear. Frequency inversion is clearly demonstrated by the diagonal stripe of high signal intensity with a negative slope (running from the upper left to the lower right corner of the figure). The weak diagonal stripe with a positive slope (from the lower left to the upper right corner) is due to weak conventional (that is, frequency conserving) reflection from inhomogeneities in the spin-wave waveguide.

Mentions: Experimental demonstration of frequency inversion in the DMC system is shown in Figure 3. The efficiency of the process is maximal in the case of fS=fa, and decreases symmetrically with positive and negative detuning (Fig. 3a). Figure 3b shows the spectrum of the reflected signal as a function of the incident signal carrier frequency fS. The spectral width of the reflected packet is of order 5 MHz—the bandwidth of the 200 ns input pulse—indicating that no significant spectral broadening is introduced in the dynamic reflection process.


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 demonstration of frequency inversion by the dynamic magnonic crystal.(a) When the carrier frequency of the incident spin-wave signal packet is detuned from the resonance value of 6,500 MHz (the bandgap centre frequency), the frequency of the reflected signal is inverted about this value (left ordinate axis, red diamonds). The solid red line is the theoretical curve of equation (2). The efficiency of the reflection process (right ordinate axis, blue circles) is maximum at the resonance condition and decreases symmetrically with detuning. (b) Two-dimensional map of reflected signal spectra as a function of the incident signal carrier frequency fS (31 spectra taken at 1 MHz intervals of fS). Dark red is indicative of the highest signal intensities, dark blue the lowest; the intervening colour scale is linear. Frequency inversion is clearly demonstrated by the diagonal stripe of high signal intensity with a negative slope (running from the upper left to the lower right corner of the figure). The weak diagonal stripe with a positive slope (from the lower left to the upper right corner) is due to weak conventional (that is, frequency conserving) reflection from inhomogeneities in the spin-wave waveguide.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Experimental demonstration of frequency inversion by the dynamic magnonic crystal.(a) When the carrier frequency of the incident spin-wave signal packet is detuned from the resonance value of 6,500 MHz (the bandgap centre frequency), the frequency of the reflected signal is inverted about this value (left ordinate axis, red diamonds). The solid red line is the theoretical curve of equation (2). The efficiency of the reflection process (right ordinate axis, blue circles) is maximum at the resonance condition and decreases symmetrically with detuning. (b) Two-dimensional map of reflected signal spectra as a function of the incident signal carrier frequency fS (31 spectra taken at 1 MHz intervals of fS). Dark red is indicative of the highest signal intensities, dark blue the lowest; the intervening colour scale is linear. Frequency inversion is clearly demonstrated by the diagonal stripe of high signal intensity with a negative slope (running from the upper left to the lower right corner of the figure). The weak diagonal stripe with a positive slope (from the lower left to the upper right corner) is due to weak conventional (that is, frequency conserving) reflection from inhomogeneities in the spin-wave waveguide.
Mentions: Experimental demonstration of frequency inversion in the DMC system is shown in Figure 3. The efficiency of the process is maximal in the case of fS=fa, and decreases symmetrically with positive and negative detuning (Fig. 3a). Figure 3b shows the spectrum of the reflected signal as a function of the incident signal carrier frequency fS. The spectral width of the reflected packet is of order 5 MHz—the bandwidth of the 200 ns input pulse—indicating that no significant spectral broadening is introduced in the dynamic reflection process.

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