Back reflection insensitive electro-optical interface and a method of coupling the same to a waveguide

An electro-optical interface with a package base having an electrical connection configuration suitable for connecting to a source of electrical signals. A semiconductor optical signal source is provided mounted to the base and having a second or higher order grating in the cavity. The signal source is operatively connected to the package base whereby the electronic signals may be converted into optical signals. A waveguide is positioned adjacent to the signal source to couple the optical signal to the waveguide. The cavity is sized, shaped and positioned so that a radiation field for the cavity is not a mode discrimination mechanism wherein any back reflections into the cavity will affect a coupling coefficient to the radiation field without significantly adversely affecting the output signal quality.