Rotational Doppler effect using ultra-dense vector perfect vortex beams

The rotational Doppler effect holds significant potential for remote sensing of rotating objects due to its real-time performance and non-contact advantages. A single-ring beam is used to measure rotation speed. To enhance the signal-to-noise ratio and measure additional parameters, multiple rings are introduced in the context of a rotational Doppler effect. However, the interference between these rings poses a challenge for multitasking detection applications. In this study, cross-polarization superposition was applied to generate an ultra-dense vector perfect vortex beam that exhibited sensitivity to spatial position and object size, and flexibility in designing topological charge combinations for generating frequency combs. A proof-of-principle experiment was conducted to demonstrate its capability in improving the signal-to-noise ratio, and accurately perceiving both the radius of rotation and radial size. An ultra-dense vector perfect vortex beam provides a general strategy for beam construction and the multi-parameter perception of rotating objects, thereby enabling potential applications in the measurement of velocity gradient measurement of fluids.