We show that the dissociation of the NH complex in hydrogenated III-N-Vs can be laser activated at temperatures that are significantly smaller than those (> 200 C) required for thermal dissociation due to a resonant photon absorption by the NH complex. This phenomenon provides a mechanism for profiling the band-gap energy in the growth plane of the III-N-Vs with submicron spatial resolution and high energy accuracy; the profiles are erasable and the alloys can be rehydrogenated making any nanoscale in-plane band-gap profile rewritable.