Diffraction engineering of multimode waveguides using computer-generated planar holograms.

The self-imaging property in multimode waveguides is related to the waveguide widths and lengths. By engineering the diffraction properties of multimode waveguides, we propose a scheme to design devices with reduced self-imaging lengths at a fixed width. Using computer-generated planar holograms, the coupling coefficients between the guided modes are adjusted to generate the desired diffraction properties. Calculations based on the coupled-mode theory are presented. Devices are designed based on a silicon-on-insulator (SOI) platform. Beam propagation simulations are used to verify the coupled-mode theory analysis.