Controllable multi-trap optical tweezers based on low loss optical phase change and metalens

A novel dual-trap and multi-trap optical tweezers are designed and analyzed, in order to enhance the particle trapping performance of optical tweezers in three-dimensional (3D) space. Firstly, a controllable dual-trap optical tweezers was proposed based on metalens and the low-loss optical phase-change material Sb<sub>2</sub>S<sub>3</sub>. The vector transverse and axial analysis of the optical force on two 250 nm radius SiO<sub>2</sub> particles were also carried out. The simulation results show that when Sb<sub>2</sub>S<sub>3</sub> is in the crystalline state, the transverse optical trap stiffness <em>k</em><sub><em>x</em></sub> of two particles reached about 25.7 pN μm<sup>-1</sup> W<sup>-1</sup> and 37.4 pN μm<sup>-1</sup> W<sup>-1</sup>, respectively, and the axial optical trap stiffness <em>k</em><sub><em>x</em></sub> is about 10.0 pN μm<sup>-1</sup> W<sup>-1</sup> for both. While when the Sb<sub>2</sub>S<sub>3</sub> is in the amorphous state, both <em>k</em><sub><em>x</em></sub> and <em>k</em><sub><em>z</em></sub> are about 1/10 of its crystalline state. As a result, the particle is not stably trapped in the <em>z</em>-direction, and thus enabled the controllability of trapping particles in 3D space. Furthermore, an array-type multi-trap optical tweezers was proposed. By regulating the crystal state and non-state of phase-change material Sb<sub>2</sub>S<sub>3</sub>, it is convenient to form different combinations of 3D trap schemes. These new optical tweezers can realize 3D space particle trap in various ways, improving the flexibility of optical tweezers, and providing series of new ways of metalens-based optical tweezers.