This letter reports the synthesis and optical characterization of GaAs nanowires obtained by oxide-assisted laser ablation of a mixture of GaAs and Ga2O3. The GaAs nanowires have lengths up to tens of micrometers and diameters in the range of 10–120 nm, with an average of 60 nm. The nanowires have a thin oxide layer covering a crystalline GaAs core with a [111] growth direction. Raman scattering and photoluminescence (PL) characterizations of GaAs nanowires reveal that the spectral peaks significantly shifted and broadened from those of bulk GaAs material. The changes in these spectra are mainly attributed to impurities, defects, and residual stress in the GaAs nanowires. © 2001 American Institute of Physics.