Theoretical Investigation On The Light Force Exerted By A Laser Beam On A Negative Index Material Sphere

Light can exert radiation pressure on objects, which was conformed Experimen-tally in the early years of the 2000s.But it was until lasers was discovered in 1960's, especially when A.Ashkin found lasers' dynamic actions on small particles, lasers and small particles were joined together. Lasers can exert radiation pressure on small particles, which were used to cool and trap neutral atoms. Lasers can also exert torque on small particles. A trap can be created in the beam waist's neighborhood from a tightly focused laser beam, dielectric particles and biological macromolecule can be trapped. Infrared light lasers are noninvasive, which can be used to trap living cells. So there is a wide application in biology.In chapter one, for particles whose size is much less than the wavelength, one is in the Rayleigh regime, the force on the particle divides itself naturally into two components:a scattering force and a gradient force. Effect of spatial coherence on radiation pressure and a pulsed Gaussian acting on a Rayleigh dielectric sphere was mentioned.In the second chapter, for a particle whose size is much larger than the wavelength, one is in the geometric optics, the analytical expressions for the longitudinal force were derived. By numerical simulation, comparisons were made between a dielectric sphere and a negative index material sphere, it is found that there are significant differences naturally and numerically.Chapter three, numerical simulations were given on the transverse force of a dielectric sphere and a negative index material sphere. Laser waist radius,relative refraction index,the radius of the sphere can influence not only the amplitude of the trapping force, but also the position of the most value, the details were discussed.