It was recently found that marked polarization anisotropy of light emission can be obtained in GaAsN/GaAsN:H planar heterostructures. This is related to anisotropic strain in the sample growth plane. The strain field is due to the formation of N-H complexes along the hydrogen diffusion profile. In the present paper, we present Raman and photoreflectance results from GaAsN/GaAsN:H micro-sized wires made by an in-plane selective hydrogen incorporation controlled by H-opaque metallic masks. The strain field was mapped by measuring the variations in GaAs-like LO phonon frequency. The experiments also allow to monitor the hydrogen diffusion profile via the Ga-N local vibrational mode line, whose quenching is related to the formation of N-H complexes. On a macroscopic scale, photoreflectance experiments provide additional evidence of the in-plane strain re-distribution.