Finite size effects on superlattice acoustical phonons studied by microcavity-enhanced Raman scattering

We use double optical resonant Raman amplification in a semiconductor microcavity to study the acoustical phonon spectra of GaAs/AlAs superlattices made of only a few periods. Besides the four orders of magnitude Raman scattering enhancement, the design allows the simultaneous collection of backward and forward-scattering contributions. The acoustical phonon spectra in the folded phonon region displays three main peaks and weaker satellites reflecting interference effects on the Raman scattering of the finite superlattice. We describe the results using a photoelastic model for the Raman efficiency which takes into account the superlattice finite size and the cavity-confined photon field.