After reading that article and other articles regarding optical traps and microscopy, it seems that the optical trapping is an automatic process? Ie. you still need the cover slides but the particles are automatically trapped by the beam.
"Optical Trapping and Coherent Anti-Stokes Raman Scattering (CARS) Spectroscopy of Submicron-Size Particles"
IEEE JoQE Vol.11 No. 4 Jul/Aug 2005