Internal field dynamics of coherent bloch oscillations in superlattices

Dekorsy, Thomas; Leisching, P.; Beck, W. P.; Ott, R.; Dhaibi, Yousef; Schwedler, R.; Roskos, Hartmut G.; Kurz, H.; Köhler, K.

doi:10.1006/spmi.1994.1003

Cited by 5 publications

(3 citation statements)

References 8 publications

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“…The amplitude of the Bloch oscillations as a function of the electric field below the cut-off frequency uco is expected to decrease like A /e F due to the increased localization of the wavefunctions. Indeed, this behaviour is observed experimentally for higher fields (Dekorsy et al 19946). The decay of the maximum amplitude of the Bloch oscillations in our experiments is also influenced by the fact that the interband absorption strength of the WS states changes with increasing field.…”

Section: E Xp Erim En Ta L Resu Ltssupporting

confidence: 78%

“…Figure 7 presents results of THz-emission studies performed with a 13 meV sampIe held at a temperature of 10 K and biased into the WS regime by an applied voltage of -1.5 V (Roskos et al 1994b). The density of the excited electron-hole pairs is 1 x 10 9 cm-2 for bandedge excitation but increases at higher photon energies because the energy of the optical excitation pulses is held constant.…”

Section: (B) Hot-carrier Excitationmentioning

confidence: 99%

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Bloch oscillations

1996

Phil. Trans. R. Soc. Lond. A

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The status quo of the research on Bloch oscillations in semiconductor superlattices is outlined. Bloch oscillations excited by femtosecond laser pulses have been investi gated by different optical techniques. They have allowed measurement of the internal electric field changes associated with the charge oscillations, the emitted terahertz electromagnetic radiation and the nonlinear coherent optical response, all directly in the time domain. The main results are summarized and critically reviewed. The potential of Bloch oscillations for practical applications in terahertz radiation sources is assessed.

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Section: E Xp Erim En Ta L Resu Ltssupporting

confidence: 78%

Section: (B) Hot-carrier Excitationmentioning

confidence: 99%

Bloch oscillations

1996

Phil. Trans. R. Soc. Lond. A

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“…Signatures of BOs have not only been observed in the FWM emission [301,302,307] but also in time-resolved transmission signals [308]. In addition, electro-optical sampling measurements have been performed that directly test the dynamics of the intraband polarization that accompanies the BOs [309][310][311]. With the latter technique, BOs have been demonstrated even at room temperature [312].…”

Section: Bloch Oscillationsmentioning

confidence: 99%

Femtosecond spectroscopy in semiconductors: a key to coherences, correlations and quantum kinetics

2004

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The application of femtosecond spectroscopy to the study of ultrafast dynamics in semiconductor materials and nanostructures is reviewed with particular emphasis on the physics that can be learned from it. Excitation with ultrashort optical pulses in general results in the creation of coherent superpositions and correlated many-particle states. The review comprises a discussion of the dynamics of this correlated many-body system during and after pulsed excitation as well as its analysis by means of refined measurements and advanced theories. After an introduction of basic concepts-such as coherence, correlation and quantum kinetics-a brief overview of the most important experimental techniques and theoretical approaches is given. The remainder of this paper is devoted to specific results selected in order to highlight how femtosecond spectroscopy gives access to the physics of coherences, correlations and quantum kinetics involving charge, spin and lattice degrees of freedom.First examples deal with the dynamics of basic laser-induced coherences that can be observed, e.g. in quantum beat spectroscopy, in coherent control measurements or in experiments using few-cycle pulses. The phenomena discussed here are basic in the sense that they can be understood to a large extent on the mean-field level of the theory. Nevertheless, already on this level it is found that semiconductors behave substantially differently from atomic systems. Subsequent sections report on the occurrence of coherences and correlations beyond the mean-field level that are mediated either by carrier-phonon or carrier-carrier interactions. The corresponding analysis gives deep insight into fundamental issues such as the energy-time uncertainty, pure dephasing in quantum dot structures, the role of twopair or even higher correlations and the build-up of screening. Finally results are presented concerning the ultrafast dynamics of resonantly coupled excitations, where a combination of different interaction mechanisms is involved in forming new types of correlations. Examples are coupled plasmon-phonon and Bloch-phonon oscillations.The results reviewed in this paper clearly reveal the central role of many-particle correlations and coherences for the ultrafast dynamics of dense semiconductor systems. Both

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Coherent phonons in condensed media

Dekorsy¹,

Cho²,

Kurz³

2000

Topics in Applied Physics

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139

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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Internal field dynamics of coherent bloch oscillations in superlattices

Cited by 5 publications

References 8 publications

Bloch oscillations

Bloch oscillations

Femtosecond spectroscopy in semiconductors: a key to coherences, correlations and quantum kinetics

Coherent phonons in condensed media

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