Stress-induced doubly resonant Raman scattering in GaAs

We have been able to produce conditions for doubly resonant Raman scattering where both incident and scattered light are simultaneously in resonance with an electronic interband transition, by fine tuning of the energy separation between light- and heavy-hole valence-band states using uniaxial stress. Under these conditions the Raman tensor for scattering by phonons becomes strongly asymmetric and forbidden scattering by TO phonons is also observed. The ability to approach the double resonance in a continuous manner allows direct comparison between experiment and theory and leads to a better understanding of these novel phenomena.