The design, microfabrication and testing of diffractive optical elements (DOE's) with continuous relief and their use in fiber coupling, is discussed in detail. DOE's with diameter as small as 65 /spl mu/m are realized by means of focused ion beam (FIB) technology. A focused Ga/sup +/ ion beam is used to mill a continuous relief microstructure at an acceleration voltage of 50 kV. From the results of the test, a coupling efficiency of 75% was achieved. This indicates that the DOE's were suitably designed within the application requirements and satisfactorily manufactured by using FIB.