Fabrication of blazed holographic gratings with two-step technique

A two-step technique of fabricating blazed holographic grating is presented. The grating fabrication includes two exposures and two developments. In the first step, two collimated laser beams with symmetrical incidence about the normal of the holographic plate generate a grating with quasi-sinusoidal groove profile after the first development. In the second step only one collimated laser beam irradiates on the plate with a selected incident angle, resulting in a change of groove profile into quasi-triangular after the second development. A blazed holographic grating with 65% relative diffraction efficiency under non-auto-collimation was obtained in the experiment. The scanning electron micrographs clearly show the quasi-triangular groove profile of the grating. The factors that affect the groove profile are discussed.