Dynamic Characteristics Of Microparticles In Vacuum Optical Tweezers

When the laser interacts with the material,the exchange of linear momentum and angular momentum will occur,so that the light force can be used to realize the suspension and rotation of the object,and the advantage is that it can be operated without contact.In the past,most of the research on light-induced rotation was carried out in water and air,but this article is carried out in the background of vacuum.In vacuum,this extremely low pressure environment can greatly reduce the friction between the environment and the object,while avoiding With the interference of the external environment,the use of vacuum optical tweezers can make the object rotate at a high speed.Therefore,it is necessary to comprehensively analyze the interaction mechanism of the three factors of light source,particle and vacuum environment.The paper is divided into three steps to realize the suspension,rotation and speed of the object.First,It is proposed to use Gaussian beam incidence to capture micro-nano spheres and disks in vacuum and make them suspended.According to the conservation of momentum,as long as it deviates from the equilibrium point,the object will always receive a restoring force toward the focal point of the light.By studying and analyzing the electric field,optical force and potential energy curves of the particles in the optical trap system,the appropriate trapping parameters are determined,including the particle radius,refractive index,and the wavelength and numerical aperture of the light source.The long-term stable capture of particles also lays the foundation for the subsequent stable rotation of the driven particles.Next,In the vacuum optical tweezers system,circularly polarized light is used to drive the particles to rotate at a high speed while capturing the object.The Maxwell stress tensor method is used to calculate the light moment of the particles at the equilibrium point.When the light moment and the damping moment are balanced,the object will rotate around the axis at a constant rotation frequency.Due to the strong focus of the light field,the spin angular momentum of the circularly polarized beam produces part of the orbital angular momentum,so that the object rotates around its axis.According to the data,when left-handed circularly polarized light is incident,the disc rotates clockwise around its axis,while right-handed circularly polarized light is the opposite.From this,it is possible to determine the rotation speed,steering,posture,and stable rotation of the particles according to the optical torque.Finally,in order to increase the rotation frequency of the disk,combining the optical power and damping coefficient data obtained by numerical simulation,discuss the phase difference of elliptically polarized light,the numerical aperture of the light source,the pressure in the vacuum environment,the translational position of the particles and other factors The effect on the light moment.In a vacuum environment,circularly polarized light is used to achieve a rotation frequency of THz for disc particles with a radius of 300 nm.In conclusion,this dissertation realizes the capture and uniform rotation of nanoparticles in vacuum,and discusses how to improve the limit rotation frequency of the rotor.High speed rotation is not only used to study the material limit test and vacuum friction under nano centrifugal force,but also provides a new idea for improving the sensitivity of optical gyroscope.