Self-rotating property of the fractional Bessel beam

The fractional Bessel beam (FBB) with an opening across multiple intensity rings and spatial stability during free-space propagation can be applied in many areas, such as optical manipulation and optical imaging. In this work, we demonstrate the self-rotating property of the FBB. The opening in the main intensity ring (OMIR) of the FBB rotates approximately 100 degrees clockwise when passing a formally unknown propagation distance. By calculating the rotation angle of the FBB's OMIR, we can obtain the corresponding propagation distance, thereby achieving the distance measurement. In addition, the measuring range of the distance measurement can be adjusted by modifying the radial wave vector of the FBB.