Simultaneous Observation of Coherent GaSb-like and AlSb-like Longitudinal Optical Phonons in GaSb/AlSb Superlattices

Enhancement of terahertz radiation from coherent optical phonons via impulsive interference of excitons in GaAs/AlAs multiple quantum wells

“…In fact, we demonstrated from the periodnumber dependence of the THz-radiation intensity that the THz wave generated in each GaAs layer is constructively superimposed [5,6]. We also note that a long dephasing time of the confined LO-phonon mode [8] leads to monochromatic THz wave. Thus, the coherent LO phonon in the MQW is a good candidate for the intense THz radiation source; however, there is a severe problem that is the fact that disturbance to coherent LO phonons by thermal phonons remarkably reduces the THz-radiation intensity at room temperature [6].…”

“…In addition, the THz radiation from the coherent LO phonon has a long dephasing time even at room temperature. The long dephasing time is due to the quantization of the LO-phonon energies because the LO-phonon decay to acoustic-phonon branches is restrained by the quantized phonon states [8]. It should be noted that we could observe no excitonic QB signal.…”

Interactions between coherent optical phonons and excitonic quantum beats in GaAs/AlAs multiple quantum wells: strategy for enhancement of terahertz radiation from coherent optical phonons

“…In addition, the THz radiation from the coherent LO phonon has a long relaxation time, which corresponds to the sharp FT band, even at room temperature: The value of full width at half maximum of the FT band is 0.17 THz in the (21, 21) MQW. The long relaxation time is due to the quantization (confinement) of the LO-phonon modes because the LO-phonon decay to acoustic-phonon branches, which determines the relaxation time, is restricted by the quantized phonon states [20]. We note that oscillations due to the excitonic QB could not be observed.…”

Terahertz spectroscopy of dynamics of coupling between the coherent longitudinal optical phonon and plasmon in the surge current of instantaneously photogenerated carriers flowing through the i-GaAs layer of an i-GaAs/n-GaAs epitaxial structure

“…We note that the time-partitioning Fourier transform has been applied to investigate the time evolution and decay time of the coherent LO phonon and LOPC mode in the optical reflection-type pump-probe measurement. [21][22][23] The time-partitioning Fourier power spectra of the terahertz waveform at the pump-beam power of 100 mW are shown in Fig. 6.…”