MEASUREMENTS OF OPTICAL TRAPPING EFFICIENCY FOR MICRON-SIZED DIELECTRIC PARTICLES IN VARIOUS SURROUNDING MEDIA

The maximum axial trapping efficiency Q(max) has been measured in wate r, ethanol, butanol and octanol for polystyrene latex spheres having a diameter of 2-15 mu m. The effects of the diameter of the particle as well as the refractive index and the viscosity of surrounding medium have been investigated. For particles of d greater than or equal to 7 mu m, Q(max) is almost independent of particle size, while it decrease s as the diameters decrease to d less than or equal to 5 mu m. It is a lso noted that Q(max) is affected by the viscosity rather than the ref ractive index of the surrounding medium.