Design of broadband multilayer diffractive optical elements with multifocal imaging

Multilayer diffractive optical elements (MLDOEs), due to their broadband optical properties, can be widely used in optical system design. However, MLDOEs only focus on one focal point, they cannot meet the requirement of broadband imaging at multifocal points which is important to multifocal broadband imaging system design. In this paper, we proposed the design principle of multifocal broadband MLDOEs. The phase distribution of MLDOEs for multifocal imaging was obtained by improving the phase of each layer. The believed to be novel design principle of multifocal MLDOEs between the diffraction efficiency of each focus and the design wavelength of each layer was revealed and analyzed. Finally, we proposed the multifocal broadband multilayer diffractive optical element results through the evaluation equation and verified by finite element method. The results showed that, through the proposed design method, high broadband diffraction efficiency under each focus was achieved. To the best of our knowledge, this research reveals the MLDOE design method for multifocal imaging and broadband. The method will extend the research and application of broadband MLDOEs into multifocal imaging area, and provide a reliable MLDOE design theoretical basis for multifocal broadband imaging systems.