ABSTRACT
Quantum Beats in Multiple Quantum Wells . . . . . . . . . . . . . . . . . . . . 153 4.6 Coherent Phonons in Superlattices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
4.6.1 Coherently Coupled Bloch-Phonon Oscillations in Biased Superlattices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
4.6.2 Coherent Excitation of Zone-Folded Acoustic Phonons by Impulsive Stimulated Raman Scattering . . . . . . . . . . . . . . . . . . . . 158
4.6.3 Propagation of Coherent Acoustic Phonons in Superlattices . . . 161 4.6.4 Coherent Acoustic Phonons in Wide-Bandgap Nitride-Based
Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
4.6.5 Coherent Acoustic Phonon Detection by Time-Resolved X-Ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
4.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
The progress in the generation of ultrashort laser pulses has always been driven by the eagerness of scientists to watch physical phenomena while they happen. As the invention of the electron microscope and scanning probe techniques have led to atomically resolved pictures of the nanocosmos, the development of femtosecond lasers has allowed us to make movies of the dynamics of electrons and vibrational excitations on timescales shorter than typical scattering times. Especially in semiconductors and semiconductor nanostructures, ultrafast time-resolved optical techniques contributed to disentangle the time constants of the most important interactions [1].
