Characterization of trapping force on metallic mie particles.

Transverse trapping force on three types of metallic Mie particles (gold, nickel, and silver) is measured for different values of the numerical aperture of an objective used for trapping. The experimental results are compared with those calculated with a modified ray-optics model. It is found that, unlike the situation for a trapped dielectric particle, the maximum transverse trapping efficiency for a trapped metallic particle is increased with the numerical aperture of the trapping objective. After consideration of radiometric force, which is caused by the heating effect, and spherical aberration, which is induced by the refractive-index mismatch, the measured results agree well with the theoretical prediction. The magnitude of the radiometric force is approximately ten times stronger than the maximum transverse trapping force.

[1]  J. P. Barton,et al.  Theoretical determination of net radiation force and torque for a spherical particle illuminated by a focused laser beam , 1989 .

[2]  X. Gan,et al.  Trapping force by a high numerical-aperture microscope objective obeying the sine condition , 1997 .

[3]  A. Ashkin.  Forces of a single-beam gradient laser trap on a dielectric sphere in the ray optics regime. , 1992, Methods in cell biology.

[4]  M. Schliwa,et al.  Calibration of light forces in optical tweezers. , 1995, Applied optics.

[5]  M W Berns,et al.  Parametric study of the forces on microspheres held by optical tweezers. , 1994, Applied optics.

[6]  Humio Inaba,et al.  Optical trapping and manipulation of microscopic particles and biological cells by laser beams , 1996 .

[7]  Stephen Arnold,et al.  Radiometric levitation of micron sized spheres , 1982 .

[8]  I. Yamaguchi,et al.  Optical trapping of metallic particles by a fixed Gaussian beam. , 1998, Optics letters.

[9]  Satoshi Kawata,et al.  Near-Field Scanning Optical Microscope with a Laser Trapped Probe , 1994 .

[10]  Y. Waseda,et al.  Optical trapping of microscopic metal particles. , 1994, Optics letters.

[11]  Michael W. Berns,et al.  Radiation trapping forces on microspheres with optical tweezers , 1993 .

[12]  Hiroshi Masuhara,et al.  Optical trapping of a metal particle and a water droplet by a scanning laser beam , 1992 .

[13]  Steven M. Block,et al.  Optical trapping of metallic Rayleigh particles. , 1994, Optics letters.

[14]  Robert C. Gauthier,et al.  Optical levitation of spheres: analytical development and numerical computations of the force equations , 1995 .

[15]  S. Kawata,et al.  Gold-bead scanning near-field optical microscope with laser-force position control. , 1997, Optics letters.

[16]  Peter Török,et al.  Electromagnetic diffraction of light focused through a planar interface between materials of mismatched refractive indices: an integral representation , 1995 .

[17]  T. Lindmo,et al.  Calculation of the trapping force in a strongly focused laser beam , 1992 .