Multi-value phase grating fabrication using direct laser writing for generating a two-dimensional focal spot array

Abstract

As a beam splitter, multi-value phase grating (MVPG) has a higher diffraction efficiency than the traditional Damman grating (DG) due to its increased number of phase values within one period of the grating. In this paper, two MVPGs are numerically designed within a 120 μm × 120 μm area, which generate 4 * 4 and 5 * 5 focal spot arrays in the far field. Both gratings are fabricated by direct laser writing (DLW) technology. Their diffraction efficiencies reach 68.58% and 63.4%, respectively. To compare, DGs with the same size and focal spot arrays are designed and fabricated, whose diffraction efficiencies are tested to be 29.55% and 35.04%, respectively. The results demonstrate the better optical properties of multi-value phase gratings and the capability of DLW in three-dimensional nano-scale diffractive optical element fabrication.