Optical Trapping Of Nanoparticals By Ultrashort Laser Pulses

Laser particle technology is use a strong focusing laser beam as light source to produce the radial forces acting on the particles to capture and manipulate particles. The optical tweezers is the single beam optical trap gradient force, focused the laser beam, the beam waist has been focusing a high field strength gradient near the forming force, the force magnitude to Newton, rely on the force to the three dimensional stability to capture and manipulation of the particles. Therefore, the laser beam is very important to research on the radial force. In recent years a large number of new types of laser beams have been applied to the research radial force acting on the particle, puts forward with ultrashort pulse laser trapping particles. So this thesis introduces the continuous wave optical tweezers and ultrashort pulse laser wave optical tweezers below are the main content of this thesis, respectively. The full text of the organizational structure as follows:1, the transmission properties of abnormal vortex beam, on the basis of detailed analysis of the abnormal focus of vortex beam under axial limitation influence on the capture of the Rayleigh dielectric ball, and discuss the abnormal vortex beams of different topological charge number and order number on the radiation effect. Based on the theory of Rayleigh scattering on the theoretical and numerical analysis of the paraxial approximation cases abnormal vortex beam radiation of nanoparticles, shows a beam with the appropriate order number and the topological charge number of strong focusing the abnormal vortex beam can be used to capture and manipulate a insulation spherical nanoparticles, the medium the refractive index of ball can be greater than or less than the surrounding environment. Also abnormal vortex beams are discussed the order number and the topological charge number of the different effect on the radial force, besides, we also analyzed the condition of stable capture Rayleigh particles.2, this thesis puts forward pulsed laser to replace traditional continuous laser pulse beam as the light source to capture the metal nanoparticles. But for pulsed laser optical tweezers capture the object of study, the present study are generally concentrated in the micron particles. This thesis theoretically analyzes the pulse optical tweezers of radial force acting on the particle, and under the precondition of stable nanoparticles capture made analysis to the requirement of pulse laser beam. Results show that for a given particle pulse interval and pulse duration ratio should be chosen strictly, in addition to some parameters also exist in the traditional continuous optical tweezers.