Abstract: A major problem for surface-relief hologram is lack of enough diffraction efficiency for different applications. Different approaches have been proposed to achieve this target including multi-level step lithography. The multi- level lithography need highly accurate mask making and etching process in order to make stepwise grating pitch profile to enhance the first order diffraction efficiency. Other methods such as gray level exposure etc. also use phase grating profile in process control. This paper proposes to utilize both gradient index thin film coating and etching processes to enhance diffraction efficiency. Moreover, this study investigates the theoretical feasibility of proposed grating structure which was made of a gradient index layer etched to form rectangular shaped binary profile pitches. This structure may be easier and more cost effective to do than multi-level lithography process. A theoretical study using rigorous coupling theory employed to do analysis was developed. The result was presented to show the effect of gradient index layer on the performance of a grating diffraction. Theoretical model shows the potential for using gradient index layer structure to enhance diffraction of surface-relief hologram. !9
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