Design of a composite multichannel beam splitting and shaping metasurface for edge-emitting lasers

In recent years, edge-emitting lasers (EELs) have gained widespread applications in many fields such as optical communication and laser processing due to their advantages of high power, high coupling efficiency, and good electrooptical conversion efficiency. However, due to the asymmetry of the waveguide structure in EELs, significant difference in divergence angles between the fast and slow axes exists in the output beam, resulting in elliptical intensity distribution in the far-field. the single-beam emission from the EEL also limits its further development in multi-channel optical systems and optical communication applications. To address these issues, this paper proposes a design method for a simultaneous multi-channel beam-splitting and shaping metasurface aimed at EELs. The phase of the metasurface is formed by the shaping phase and the multi-channel beam-splitting phase, in which the shaping phase is the superposition of the phases of two orthogonal cylindrical lenses while the beam-splitting phase is achieved by superimposing the phases of multiple diffraction orders of a grating. By multiplexing combinations of these phases, multi-channel beam-splitting and shaping of the EEL's emitted light can be simultaneously achieved with arbitrarily designed M×N multi-channel split and shaped beams. Simulation results show that the aspect ratio of the split spot can be reduced from 4.039 to 1.0424 after shaping for a typical EEL with λ=980 nm and divergence angles in the fast and slow axes of θ_f=35° and θ_s=14°, resulting in a circular spot shape. The proposed composite-function metasurface is of lightweight, high-efficiency, and high integration for optical systems, and holds great potential for applications in optical communication, laser processing, and other fields.