A device for achromatic input coupling of an optical beam into a waveguide is disclosed. The device includes a waveguide formed of a material having an effective index of refraction and having first and second surfaces, such waveguide defining a guided mode of propagation. A first grating is provided at the interface at the first surface of the waveguide, such first grating being selected so as to diffract an optical beam at an appropriate angle selected so that the beam is coupled into the guided mode of the waveguide. A second waveguide is provided at the interface at the second surface of the waveguide, such second grating selected so as to diffract a beam to provide an appropriate angle of incidence onto the first grating at the first surface waveguide. An important aspect of the present invention is the use of linear dispersion of the gratings to cancel the linear portion of the sum of the intrinsic waveguide dispersion and the material dispersions of the waveguide and the prism.