Quarter-wave optical filters

Figure 10. Optical configuration for differentially arranged, thermal lens detected CD. P, beam steering prism M, beam steering mirror BS, polarizing beam splitter HR, half-wave rhomb QR, quarter-wave rhomb L, focusing lens DM, dichroic mirror C, converging sample cell (before probe focus) D, diverging sample cell (after probe focus) PD, aperture/photodiode combination LF, line filter (to isolate the probe laser from extraneous pump radiation). Solid line, probe laser optical path broken line, pump beam path.

Figure lb, c illustrates the optical configuration of objective-type TIRFM on an inverted microscope see Note 1). An objective lens with high numerical aperture (>1.4) is mounted on the inverted microscope (rrrNote 2). Alaser beam is passed through a neutral density filter and a beam expander to adjust its power and diameter. In order to convert the polarization of the beam from linear to circular, we used a quarter-wave plate. The incident laser beam is focused on the back focal plane (BFP) of the objective (rrrNote 3). To perform singlemolecule imaging, a laser beam is incident to the specimen at a power of 1 mW on a circular area 30 pm in diameter. 

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