Manipulate and detect the rotation speed of particles simultaneously using perfect vortex

Abstract

Optical vortex is a kind of unique structure light with a helical phase distribution and contains orbital angular momentum. It has been found a myriad of important applications of optical vortex, such as micromanipulation, remote sensing and communication. In recent years, there are many researches on the particle manipulation based on the orbital angular momentum of optical vortex. Especially, there is a new kind of optical vortex which is so-called “perfect” vortex whose ring radius is independent of its topological charge has an outstanding performance on the micromanipulation. However, the exist experiments can only realize manipulation of particle and the rotation speed is difficult to obtain. In this paper, we proposed a new scheme which can manipulate the particle and simultaneously detect its rotation speed. We employ the superposition perfect vortex as the probe beam. It is worth to note that the topological charge of the perfect vortex we used has an opposite sign and different magnitude. Therefore, the probe beam possesses remaining orbital angular momentum and can generate the rotational Doppler effect. The rotational Doppler effect is the basics of rotation speed detection. A corresponding experiment has been conducted to verify our method. The results have confirmed the existence of orbital angular momentum of superposition optical vortex with different topological charge. Our scheme can realize manipulation and detection the rotation speed of the particle simultaneously. It is an important supplement on the micromanipulation and maybe useful in the optical gyroscope technique.