Optical Coupling Performance in Free Space Based on Grating-Type Optical Waveguide
Spatial optical couplings in atmospheric turbulence channels are associated with low efficiencies and difficult alignments,hence,in this study,a research scheme for coupling a turbulent signal beam into optical waveguides through a grating was proposed and the influence of atmospheric turbulence on spatial light and optical waveguide coupling parameters was analyzed.Moreover,a highly efficient spatial optical coupling waveguide chip was designed by optimizing the structural parameters of the grating.Additionally,three sets of Si/SiO2 mirrors were introduced to reduce the downward coupling loss and further improve the grating coupling efficiency.Simulation results show that for the spatial light affected by atmospheric turbulence,the coupling efficiency of the incident grating coupler at 1550 nm was 74%(50.5%,without adding the mirrors)when the grating period,etching depth,and lower cladding thickness were 660 nm,100 nm,and 1.45 μm,respectively,indicating the efficient coupling of spatial light in the atmospheric turbulent channels.The findings of this study will be of great significance in improving the communication efficiency and photoelectric integration in the field of free-space optical communication.
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