Raman spectroscopy of semiconductor nanostructures in optically confined microcavities

We use a novel double microcavity for double optical resonant Raman amplifi cation. The observed four orders of magnitude Raman enhancement is exploite d 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(parallel to) dispersion of t he 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(parallel to) dispersion and success ively 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. (C) 2001 Elsevier Science B.V. All rights reserved.