The trapping beam is directed to the back aperture of a 100× NA=1.42 oil immersion objective via two lenses (L3, L4), linearly polarized by a half wave plate and polarizer and fed into the microscope ...

The beam passes through the shutter and is then directed to the back aperture of the objective using a dichroic mirror and focused within the bulk of the monomeric sample. An oil-immersion objective ...