The Design,Fabrication And Experimental Research Of Four-beam Optical Trap Chip

Optical trap is a technology which can capture and manipulation particles ranging in size from nanometers to microns by using the mechanical effect of light.It can control the movement of particles,which makes it more convenient for people to observe the dynamic process of a single particle,which is of great significance to study the individual behavior of particles.Optical trap can be divided into single-beam optical trap,dual-beam optical trap and multi-beam optical trap,etc.Dual-beam optical trap has simple structure,and it is easy to integrate.But its axial capture ability is poor.In this paper,four-beam optical trap is used to capture and control particles.Four-beam optical trap not only keeps the advantages of easy integration of dual-beam optical trap,but also greatly improves its axial optical trap stiffness and its axial capture stability.In addition,the orbit rotation of the captured microspheres was realized by modulating the trapping power of four-beam optical trap.In this paper,we combine the multi-beam optical trap with the integration technology,which improves the capture stability,enriches the realization of the photo-orbital rotation,and is of great significance for the development of the optical trap and its integrated application.Firstly,by using the ray optics(RO)method,the axial and transverse optical trap stiffnesses and forces of dual-beam optical trap and four-beam optical trap with different trapping power were calculated and analyzed.The simulation results show that the axial optical trap stiffness of four-beam optical trap is much greater than that of the dual-beam optical trap,which means four-beam optical trap can greatly improve the poor axial trapping ability of dual-beam optical trap.In addition,the axial trap stiffness of four-beam optical trap and the transverse trap stiffness of dual-beam optical trap are basically the same.The movement of the microsphere from entering the capture room to capturing was simulated,and the motion law of the capturing process of microspheres was determined: firstly,the microsphere will be captured by one of the optical channels,and then it will move to the center of the optical trap along the optical channel.Secondly,the four-beam optical trap chip and dual-beam optical trap chip were designed and fabricated.Polystyrene microspheres with radius of 5 (?)m were captured through the optical trap chip.Optical trap stiffnesses were calibrated by mean square displacement method(MSDM).The simulation results were verified by experiments,and the result of experiments prove that four-beam optical trap can improve the axial optical trap stiffness of the dual-beam optical trap,and has a stronger capture stability.Thirdly,on the basis of four beam optical trap,the orbit rotation of polystyrene microspheres was realized by modulating the input laser power.The influence of modulation frequency,modulation phase and other parameters on the trajectory were studied: when the modulation power function is a trigonometric function of the same frequency,the trapped microsphere would rotate along an elliptical trajectory;when the modulation power function is a trigonometric function with a double frequency relationship,the microsphere will rotate in a spindle like orbit.The orbital rotation frequency of microspheres is equal to the modulation frequency,and the amplitude of orbital rotation decreases with the increase of modulation frequency;at the same time,the direction of orbital rotation of microspheres will change with the different modulation phase.