method and apparatus are disclosed for making integrated optical circuits . a waveguide in the form of a thin layer of dielectric material is modified as to its coherent radiation transmitting properties by electron beam impingement thereon so as to modulate coherent radiation by mode conversion and mode guiding . preferably the layer is of thermoplastic material which is locally charged by the electron beam and is heated to allow corresponding deformation due to the forces generated by the localized charging . when cooled , the deformations are frozen in but may be erased by subsequent reheating whereafter the deformation process may be repeated , thus allowing reuse of the device for a different optical circuit , or allowing its modification to form a different optical circuit .