Trapping of dielectric particles and cells by a fiber-coupled laser trap

The laser for an optical trap can be coupled into the microscope via a sort of telescope (conventional coupling) or via optical fibers. The latter coupling results in high mechanical vibration resistance of the system and allows easy exchange of lasers. At a given laser power, coupling via fibers with a diameter below a critical value allows trapping of polystyrene beads even when trapping after conventional coupling is not possible. This is particularly the case when no cover slide can be used. With biological cells such as erythrocytes and NC 37 lymphoblastoids the differences between fiber coupling and conventional coupling are less pronounced.