Sensitivity of Displacement Detection for a Particle Levitated in the Doughnut Beam

TL;DR

This paper investigates how different doughnut-shaped laser beams affect the sensitivity of detecting particle displacement, showing that with optimal vortex charge, doughnut beams can surpass Gaussian beams in precision, especially for larger particles.

Contribution

It introduces a comparative analysis of displacement detection sensitivity using doughnut beams versus Gaussian beams, highlighting the potential for enhanced measurement precision.

Findings

Doughnut beams can outperform Gaussian beams in sensitivity for large particles.

Optimal vortex charge enhances detection sensitivity significantly.

Using doughnut beams for particle detection can aid in reducing light absorption in levitation applications.

Abstract

Displacement detection of a sphere particle in focused laser beams with quadrant photodetector (QPD) provides a fast and high precision way to determine the particle location. In contrast to the traditional Gaussian beams, the sensitivity of displacement detection using various doughnut beams are investigated. The sensitivity improvement for large sphere particles along the longitudinal direction is reported. With appropriate vortex charge $l$ of the doughnut beams, they can outperform the Gaussian beam to get more than one order higher sensitivity and thus have potential applications in various high precision measurement. By using the levitating doughnut beam itself to detect the particle displacement, the result will also facilitate the recent proposal of levitating a particle in doughnut beams to suppress the light absorption.