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. 2013 May 21;4:1878. doi: 10.1038/ncomms2882

Figure 1. Schematic and optical layout of the instrument.

Figure 1

(a) Schematic of experimental setup. One end of a DNA construct is immobilized on the polyethylene glycol (PEG)-coated surface, and the other end is attached to a polystyrene bead confined in the optical trap (pink). Green excitation laser selectively illuminates molecules within a few hundred nanometres from the coverglass surface by TIR. (b) Optical layout of the instrument showing light pathways for 532-nm fluorescence excitation laser (green), 1,064-nm trapping laser (pink) and fluorescence emission (orange). The intensities of both the fluorescence excitation laser and the trapping laser are modulated by half wave plates (WP) and polarizing beam splitters (PBS). Two beams are combined at the dichroic mirror D1 and enter into the microscope. Trapping laser light scattered by a bead confined in the optical trap is imaged on to the quadrant photodiode detector (QPD) for monitoring the position of the trapped bead. The sample on the piezo stage is illuminated by objective-type TIRF, and the fluorescence emission is collected by an EMCCD (electron-multiplying charge-coupled device) camera. D1-3, dichroic mirrors; F1-2, filters; T1, a telescope.