Gallium nitride nano superstructure and preparation method thereof and gallium nitride-based laser

A gallium nitride-based laser, comprising a gallium nitride-based laser body and a gallium nitride nano superstructure wherein the gallium nitride nano superstructure is arranged at a front end of a light-emitting end face of the gallium nitride-based laser body, and an included angle between a wire grid direction of the gallium nitride nano superstructure grating and a polarization direction of the light-emitting of the gallium nitride-based laser body is 45°;

• wherein the gallium nitride nano superstructure is used for realizing circularly polarized light output of the gallium nitride-based laser, the gallium nitride nano superstructure comprising, from bottom to top:
• a substrate, a dielectric film layer and a nano-grating structure layer:
• wherein a grating material of the nano-grating structure layer comprises one of gallium nitride, N-type gallium nitride and P-type gallium nitride, a grating period is in a range of 100 nm-280 nm, a grating height is in a range of 100 nm-300 nm, and a grating line width is in a range of 50 nm-200 nm.