Fig. 2: Optically detected transport of spins in planar quantum wires.

a Sidewall quantum wires (QWRs) formed by the epitaxial overgrowth of a quantum well (QW) on a GaAs (001) substrate structured with shallow ridges³⁰. The QWRs are 200 nm-wide and have a length defined by photolithography, which is typically several tens of microns long. Photoexcited carriers are transported along the QWR by surface acoustic waves (SAWs) generated by interdigital acoustic transducers (IDTs). b Photoluminescence (PL) spectra recorded outside (red) and on (black) a ridge sidewall showing the emission lines of the QW (1.548 eV) and QWR (1.521 eV), respectively. c–e Profiles of the right (black, \({I}_{PL}^{\circlearrowleft}\)) and left (red, \({I}_{PL}^{\circlearrowright}\)) circularly polarized PL along the QWR axis (x_QWR coordinate) recorded under the configuration illustrated in the upper panel (c) in the absence and (d, e) under a SAW. The PL was excited by a right-circularly polarized laser spot focused at x_QWR = 0 for (c) and (d), and at x_QWR = 4.5 μm for (e).