Structured-light displacement detection method using split-waveplate for dual-beam optical tweezers

Structured-light displacement detection method is an innovative approach with extremely high sensitivity for measuring the displacement of a levitated particle. This scheme includes two key components, a split-waveplate (SWP) and a single-mode fiber. In this work, we further investigated the influence of SWP installation on this method regarding the sensitivity of displacement detection. The results indicate that the sensitivity increases with the expanding of SWP offset in the effective range. In addition, we found this method has a significant tolerance rate, with an extensive SWP offset effective range of 5%-25%. However, an excessive offset can render this method ineffective. More interestingly, we demonstrated the feasibility of rotating the SWP to detect displacement in different directions. Our research contributes to guiding the structured-light detection methods in practical applications and expanding their applications in fundamental physics.