Raman spectroscopy of semiconductor nanostructures in optically confined microcavities

We use a novel double microcavity for double optical resonant Raman amplification. The observed four orders of magnitude Raman enhancement is exploited to study finite size effects on the phonon spectra of GaAs/AlAs MQWs. The design allows almost backscattering geometries, thus providing easy access to the excitations in-plane dispersion. The k|| dispersion of the GaAs-like optical phonons has been mapped out, showing the existence of a new type of “standing optical vibrations” in the Raman spectra. The N=1 order standing wave displays a giant k|| dispersion and successively anticrosses with the higher order m=5,7,9 and 11 confined phonons. The acoustic phonon spectra in the folded phonon region displays a complex series of peaks reflecting coupling effects between the two embedded MQWs.