Effect of spherical aberration introduced by water solution on trapping force

Trapping force of an optical tweezers system with an oil immersion objectiv e is calculated with a ray-optics model. Results indicate that the trapping force will be decreased as a result of the introduction of spherical aberr ation, which is caused by the refractive mismatch between objective oil and water, when the sample manipulated is suspended in a water solution. The e ffect of spherical aberration will be serious when the detection depth of t he optical tweezers is enhanced.