Center-of-mass quantization of excitons in GaAs quantum-well wires

We have studied wide quantum-well-wire structures by polarization-dependent photoluminescence and photoluminescence excitation spectroscopy. We observe an up-to-threefold splitting of the lowest heavy-hole-excition resonance, which arises from a quantization of the excitonic center-of-mass motion perpendicular to the direction of the wires. The energy separation between these transitions depends on the active wire width ${\mathit{L}}_{\mathit{x}}$, which is significantly smaller than the geometrical wire width. Identifying the exciton wave vector ${\mathit{K}}_{\mathrm{ex}}^{\mathit{n}}$ with nπ/${\mathit{L}}_{\mathit{x}}$, we can reconstruct the exciton dispersion and find excellent agreement with theory if we use the k=0 heavy-hole mass.