Coherent Phonon Dynamics Studied by Impulsive Stimulated Raman Scattering

Frequency and temperature dependence of the TO phonon-polariton decay in GaP

“…Recently we have shown that the TO phonon polariton in the investigated frequency range decays into a TA ͑upper branch͒ plus a LA phonon at the K point of the Brillouin zone. 20 Accordingly the values of 1 and 2 were chosen to be 153 and 212 cm Ϫ1 , respectively. The experimental data for the qϭ20 500-cm Ϫ1 and the 25 000-cm Ϫ1 mode exhibit either a systematically higher (20 500 cm Ϫ1 ) or lower (25 500 cm Ϫ1 ) dephasing rate than calculated by Eq.…”

Wolfgang Richter: His Resonance as a Raman Scatterer

“…(5). The resonance data he obtained for Sb have recently been used for interpreting coherent phonon generation and detection in this interesting semimetal [21].…”

“…It has never happened again. In Campinas Wolfgang presented two papers, one on the E 1 and E 1 þ D 1 resonances in semiconductors, in particular the uniaxial stress effects mentioned above, [20], the other on second-order Raman scattering (scattering with creation of two phonons with equal (in length) but opposite q vectors [21]). The question of resonant scattering by two (or more) phonons has occupied many Raman scatterers throughout the world to the present day.…”

Resonant excitation of coherent phonons in CdTe/sub 1-x/Se/sub x/ quantum dots

“…Alternative non-Raman mechanisms have been proposed involving various processes which operate on a time scale faster than the phonon period. 30 Although most of the reported resonant experiments in absorbing materials clearly support the predictions of SRS, 27,28,31,32 the apparent absence of non-fully symmetric phonon modes in early experiments 33 motivated the development of an alternative model called displacive excitation of coherent phonons. 24,25 Recently, it has been demonstrated that SRS is determined not by one but by two different tensors, one of which is the standard Raman susceptibility tensor, (the same one that gives the cross section for spontaneous RS), and a second one, , associated with the driving force of Q.…”

“…The question of the mechanisms responsible for the generation of coherent phonons with ultrafast laser pulses has been extensively discussed in the literature in recent years. [23][24][25][26][27][28][29] While it is generally agreed that SRS is the driving force for the coherent phonon field Q in the spectral region where materials are transparent, there is still a controversy as to the underlying mechanism (or mechanisms) in the opaque regime. Alternative non-Raman mechanisms have been proposed involving various processes which operate on a time scale faster than the phonon period.…”