The invention relates to a device for introducing light into a waveguide, which device comprises: a light source, preferably an electro-optical converter, more preferably a VCSEL, for generating a light beam; a reflector for receiving at least a part of the light beam and for reflecting at least a part of the received part, wherein the waveguide and the material layer lie substantially mutually in line and both rest at least partially on a substantially flat substrate, wherein the light source and the reflector are positioned relative to the waveguide such that at least a part of the reflected part is introduced into the waveguide.