Optimization
Beam must be aligned to travel exactly vertically through microscope
For best trapping, beam should be spherical
Optimal beam size overfills the objective slightly FWHM 6 mm for our setup (Amendola, 2001)
Microscope objective does not collect light from infinity, so a lens should focus light 160 mm behind the objective
Trapping most easily achieved with moving objects; surfactants used in bead solutions