Techniques for amplitude to phase conversion of binary holograms

This paper reports briefly on design and fabrication of surface relief grating beamsplitters using advanced plotting techniques such as electron beam lithography. The authors describe techniques for converting these amplitude gratings into phase-only elements hence increasing their diffraction efficiencies to >60%. These techniques include reactive ion-etching of materials such as quartz to fabricate a range of elements, the largest of which is a 201 × 201 grating beamsplitter. Interferometric and non-inferometric holographic techniques have been employed to generate phase-only grating beamsplitters in dichromated gelatin and bleached silver halide holographic plates which has resulted in fabrication of multifunctional, compact and inexpensive components. by exploiting the phase jumps which occur due to reflection at metal/glass boundaries, together with total internal reflection of glass/air interface, a novel and simple technique to generate binary-phase wavefronts directly from an amplitude mask has been developed.