Coherent phonon oscillations in GaAs

Kuznetsov, Alex V.; Stanton, C. J.

doi:10.1103/physrevb.51.7555

Cited by 147 publications

(141 citation statements)

References 22 publications

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“…This feature stems from the excitation of coherent plasmon-phonon coupled modes in the highly doped cladding layers of the p-i-n diode [21,22]. This contribution is the same at low and high fields thus strongly suggesting that it is independent of the bias applied.…”

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confidence: 81%

Coupled Bloch-Phonon Oscillations in Semiconductor Superlattices

et al. 2000

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We investigate coherent Bloch oscillations in GaAs͞Al x Ga 12x As superlattices with electronic miniband widths larger than the optical phonon energy. In these superlattices the Bloch frequency can be tuned into resonance with the optical phonon. Close to resonance a direct coupling of Bloch oscillations to LO phonons is observed which gives rise to the coherent excitation of LO phonons. The density necessary for driving coherent LO phonons via Bloch oscillations is about 2 orders of magnitude smaller than the density necessary to drive coherent LO phonons in bulk GaAs. The experimental observations are confirmed by the theoretical description of this phenomenon [A.W. Ghosh et al., Phys. Rev. Lett. 85, 1084(2000].

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confidence: 81%

Coupled Bloch-Phonon Oscillations in Semiconductor Superlattices

et al. 2000

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“…H o wever, the subpicosecond surface eld dynamics also in uences the coherent phonon amplitude detected via Eqn. (11). Figure 9 shows the dispersion of the electro-optic and of the Franz-Keldysh contribution derived from the detection of coherent LO phonons at di erent laser energies, i.e.…”

Section: R(50 Fs)mentioning

confidence: 99%

“…LO )E(!)) (11) where E surface (0) is the surface eld, E phonon (! LO ) the eld associated with the coherent LO phonons, and E(!)…”

Section: R(50 Fs)mentioning

confidence: 99%

“…The emission characteristics can be assumed to follow the emission of a dipole, which is set-up by the volume in which coherent phonons form a macroscopic polarization. The pointing vector of the radiation is given by 11] S(t) = ! 4 phonon P 2 (t) sin 2 16 2 0 r 2 c 3 s (9) where is the angle between the direction of observation s and the polarization P, and r is the distance to the detector.…”

Section: Coherent Phonon Generationmentioning

confidence: 99%

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Coherent phonons in condensed media

Dekorsy¹,

Cho²,

Kurz³

2000

Topics in Applied Physics

136

127

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Abstract. The impulsive excitation and phase-sensitive detection of coherent phonons and phonon-polaritons provide a detailed insight i n to the dynamical properties of matter. The experiments are based on optical pump-probe techniques with femtosecond time resolution. These techniques enable the detection of amplitude and phase of the coherent lattice motion simultaneously. F requencies in the THz range and dephasing times in the picosecond range can be obtained with high accuracy. Especially in semiconductors and semiconductor heterostructures, where a coherent phonon mode and free carriers are excited simultaneously, important information about carrier-phonon interaction far away from equilibrium is obtained. This paper presents an overview of recent a c hievements in this vivid eld of condensed matter physics.

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“…For the interpretation of the plasmon-phonon-coupled mode, one has to consider that we excite a nonequilibrium carrier distribution that is strongly inhomogeneous due to the spatial variation of the intensity over the focus of the pump beam. 18,19 However, at high densities the frequency of the lower phonon-plasmon mode approximately equals the TO frequency ͑8.05 THz, for qϭ0͒ over a large range of densities. Hence, the spatial inhomogeneity hardly leads to a smearing out of the oscillations of the lower phonon-plasmon mode.…”

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Time-resolved observation of coherent phonons by the Franz-Keldysh effect

et al. 1996

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We report on the time-resolved observation of coherent optical phonons in GaAs by the Franz-Keldysh effect. This effect leads to a modulation of the optical interband transitions with a nonlinear dependence on the macroscopic electric field associated with the coherent phonons. We find that the nonlinear electro-optic effect forms a far more efficient detection mechanism for coherent phonons than the linear electro-optic effect near the band gap.In recent years, the study of coherent phenomena with ultrashort laser pulses has become a matter of growing interest. The use of subpicosecond laser pulses allows a direct observation of coherent vibrations in molecules, 1 phonons in solid-state materials, 2-4 and electronic wave-packet oscillations in quantum-well structures in the time domain. 5 In previous studies the excitation mechanisms and the dephasing of coherent oscillations have been addressed.Recent investigations of coherent phonons in solid-state materials have shown that the excitation results from the impulsive interaction of the material with laser pulses whose durations are shorter than the period of the oscillation. In molecules, coherent vibrations can be excited by impulsivestimulated Raman scattering processes. 1 In narrow-band-gap semiconductors, the strong interband excitation of carriers leads to the excitation of coherent phonons by the impulsive elongation of the bonds. 3 It was found that in these materials the breathing mode of the coherent lattice vibrations modifies the band gap via the deformation potential. 6 In III-V semiconductors, the femtosecond excitation of free carriers results in the impulsive screening of the surface depletion field due to an ultrafast charge separation. This mechanism generates coherent longitudinal optical ͑LO͒ phonons, which are associated with an oscillating macroscopic electric field. 2,7 These field changes have been observed in timeresolved reflectivity measurements via the linear electrooptic effect. 2 In principle, the reflectivity changes induced by coherent phonons in III-V semiconductors arise from the modulation of the optical susceptibility at the phonon frequency, which is expressed by the coupling of the Raman tensor with the coherent motion of the atomic displacement. In a first-order approximation the phonon-induced reflectivity changes ⌬R can be described bywhere is the real part of the optical susceptibility, Q the atomic displacement, and F the macroscopic electric field. The first and second terms at the right-hand side in Eq. ͑1͒ are the deformation potential and the electro-optic contribution, respectively. This first-order Raman tensor determines the usual allowed Raman scattering with its specific polarization selection rules. 8,9 However, in the vicinity of critical points in the electronic band structure, nonlinear effects such as forbidden Raman scattering and electric-field-induced Raman scattering by LO phonons become strongly enhanced. 8,9 The polarization selection rule for these types of Raman tensors is different from that of a...

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Coherent phonon oscillations in GaAs

Cited by 147 publications

References 22 publications

Coupled Bloch-Phonon Oscillations in Semiconductor Superlattices

Coupled Bloch-Phonon Oscillations in Semiconductor Superlattices

Coherent phonons in condensed media

Time-resolved observation of coherent phonons by the Franz-Keldysh effect

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