Dynamics of coherent plasmon-phonon coupled modes in GaAs using ultrashort laser puises

Hase, Muneaki; Mizoguchi, K.; Harima, Hiroshi; Miyamaru, Fumiaki; Nakashima, S.; Fukasawa, Ryoichi; Tani, Masahiko; Sakai, Kiyomi

doi:10.1016/s0022-2313(97)00181-6

Cited by 19 publications

(20 citation statements)

References 5 publications

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“…10, the authors assigned the component at 8. 15 THz to an out-of-plane counterpropagating mode of the Ga-As bond between a Ga dimer and As atoms in the second layer, whose frequency is higher than that of the intrinsic mode because of coupling with the electric field associated with the displacement. The similar surface phonon mode should be at the GaAs(100)-c(8ϫ2) surface, and is supposed to be the origin of the main feature of the ␤ component.…”

Section: A Origins Of the Oscillatory Componentsmentioning

confidence: 98%

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Coherent surface phonon at aGaAs(100)−c(8×2)surface

et al. 2002

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Coherent surface phonon at a GaAs(100)-c(8ϫ2)-Ga reconstructed surface has been investigated by timeresolved second-harmonic generation ͑TRSHG͒. The phonon mode is impulsively excited by an ultrashort laser pulse and subsequent coherent nuclear motion is monitored through the intensity modulation of the second harmonics of a probe pulse. Oscillatory traces are clearly observed in TRSHG signals and their Fourier transformation show two peaks at 8.2-8.6 and 8.9 THz. Fitting these traces with two oscillatory components shows that the oscillatory signals are contributed by the bulk LO phonon at 8.8 THz and the surface phonon at 6.0-8.6 THz. The relative amplitude of the surface phonon modes is sensitive to sputtering and annealing of the surface. Clear dips appear at 8.7 THz in the Fourier spectra, which is caused by the initial phase difference between the surface phonon and the bulk phonon modes. The frequency of the surface component shows red shifts as the pumping power increases. The shifts are indicative of a marked electron phonon interaction or anharmonicity of the surface phonon modes.

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Section: A Origins Of the Oscillatory Componentsmentioning

confidence: 98%

“…5. GaAs 14,15. Its lower ͑L Ϫ mode͒ and the higher branch ͑L ϩ mode͒ change their frequencies from 7 to 8 THz (L Ϫ ) and from 10 to 15 THz (L ϩ ) as the carrier concentration increases from 1ϫ10 17 cm Ϫ3 to 1ϫ10 18 cm Ϫ3 .…”

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confidence: 99%

Coherent surface phonon at aGaAs(100)−c(8×2)surface

et al. 2002

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“…When coherent phonons are generated with 800 nm excitation near the fundamental band gap of GaAs [8,30], the damping is lower because the momentum scattering rate for the electrons in the Γ valley is slower than for excitation at 400 nm where it is much faster due to the increased DOS in the L and X valleys. In the low damping case, there is no solution of Eq.…”

Section: Modeling the Transient Oscillations Representing The Interacmentioning

confidence: 99%

“…The coherent coupled mode dynamics for photoexcitation of carriers across the fundamental E 0 gap of GaAs are already well understood from the pioneering work of Kurz, Dekorsy, and others [8,[28][29][30][31]. At the fundamental gap, the electrons and holes are photoexcited near the conduction band minimum and valence band maximum both at the Γ-point, where they remain until they recombine across the gap on a time scale that is much longer than the phonon dephasing time.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast coupling of coherent phonons with a nonequilibrium electron-hole plasma in GaAs

et al. 2015

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Abstract:We present a joint experimental-theoretical study of the coupling of coherent phonons in bulk GaAs with a nonequilibrium electron-hole plasma following photoexcitation at the E 1 gap by ultrafast laser pulses. In contrast to prior coherent phonon experiments where photoexcitation across the E 0 gap generated electrons in the Γ valley, for the E 1 gap excitation, the majority of the electrons are generated in the satellite L valleys. This leads to a drastically different situation from the previous studies where the damping of electrons is faster due to the higher scattering rates in the L valley and in addition, the diffusion of carriers has a significant effect on the plasma response due to the shorter optical absorption depth of the pump-probe light. Reflectivity measurements show coherent phonon-plasmon oscillations, whose frequencies are indicative of the heavy damping, which leads to coupled-mode frequencies that lie between the transverse and longitudinal optical phonon frequencies and change with time due to the diffusion of the plasma. We analyze the experimental data with a theoretical model that describes the time and densitydependent coupling of the coherent phonon and the electron-hole plasma as the photoexcited carriers diffuse into the sample on a sub-picosecond time scale. The calculated phonon-plasmon dynamics qualitatively reproduce the experimentally observed time-dependent frequency.

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“…Next, we investigated the time-evolution of the THz waveform A(t) using a time-partitioning Fourier transform method [12,13], which is a powerful way to investigate the decay process. The time-partitioning Fourier power spectrum I(ω), where ω is a frequency, is given by .…”

Section: Contributedmentioning

confidence: 99%

Simple strategy for enhancing terahertz emission from coherent longitudinal optical phonons using undoped GaAs/n ‐type GaAs epitaxial layer structures

Takeuchi

Yanagisawa

Tsuruta

et al. 2010

Phys. Status Solidi (c)

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We have explored the feasibility of enhancing terahertz (THz) emission from coherent longitudinal optical (LO) phonons using simple epitaxial layer structures: undoped GaAs/n ‐type GaAs (i ‐GaAs/n ‐GaAs) epitaxial layer structures. Initially, using a numerical simulation we have confirmed that a decrease in the i ‐GaAs layer thickness d increases the built‐in electric field in the i ‐GaAs layer. From the THz wave measurement, it is observed in the THz waveforms of the samples that the monocycle oscillation, the so‐called first burst, resulting from the surge current of the photogenerated carriers, accompanies with a clear oscillatory profile with a period of 113 fs corresponding to the GaAs LO phonon frequency (8.8 THz). The Fourier transform spectra show that the intensity of the LO phonon band remarkably increases with a decrease in d that causes the enhancement of the built‐in electric field in the i ‐GaAs layer. Thus, we conclude that the utilization of the i ‐GaAs/n ‐GaAs structure is a useful way to enhance the THz emission from the coherent LO phonon. We also performed the time‐partitioning Fourier transform in order to investigate the decay time of the THz wave from the coherent LO phonon. The decay time of each sample is almost the same: 2.0 ps. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Dynamics of coherent plasmon-phonon coupled modes in GaAs using ultrashort laser puises

Cited by 19 publications

References 5 publications

Coherent surface phonon at aGaAs(100)−c(8×2)surface

Coherent surface phonon at aGaAs(100)−c(8×2)surface

Ultrafast coupling of coherent phonons with a nonequilibrium electron-hole plasma in GaAs

Simple strategy for enhancing terahertz emission from coherent longitudinal optical phonons using undoped GaAs/n ‐type GaAs epitaxial layer structures

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