Mask designs for multiple-holographic-grating optical devices

Abstract

In this paper, we propose and examine mask design methods for fabricating optical devices containing multiple holographic gratings. As the conventional fiber Bragg grating fabrication, the mask is also required to achieve compactness and accuracy in this case. However, for the case where there needs multiplexing of several holographic gratings in the same volume of the recording medium, the mask should provide multi-order diffractions and control their relative diffraction efficiencies. We propose two methodologies for the required mask, cascaded phase mask and polymeric angularly multiplexed holographic mask. The cascaded phase mask is composed of the multi-order generating mask and the Bragg mask of two-order diffraction. The polymeric angularly multiplexed holographic mask is a kind of commonly referenced multiplexed holograms. The mask design and fabrication processes are examined. Multiple holographic grating recording in the photorefractive crystal with designed mask is discussed. In order to exclude cross diffraction order modulations, there needs to control the density of acceptors in photorefractive crystal case.