The azimuthally polarized beam always keeps a zero intensity at the center of the doughnut shaped pulse. As a result, it
can be utilized to overcome the problem of not perfect zero in STED microscopy to exhibit a high resolution. This paper
examines the utilization of this beam as the stimulated emission depletion pulse in STED microscopy and the results are
compared with the effects of using a doughnut model generated by the linearly polarized lights with inserting the phase
plates in lights. The calculations show that the azimuthally polarized beam has a great potential in the STED microscopy.
Total internal reflection fluorescence microscopy (TIRFM) was used to image single molecules with evanescent waves.
The molecules were excited by an evanescent wave with different intensities. Single molecules were imaged on
low-noise high-quantum-yield charge-coupled device (CCD) cameras. Two-step photobleaching behavior was observed.
Duration from fluorescent spots appearing to disappearing was counted. The duration was decided by the speed of
photobleaching. Peak intensity was counted as exciting intensity change. The proportion relationship between the
reciprocal of duration and exciting intensity was obtained. The emitted intensity and duration of fluorescein were
compared with GFP. A single molecules emit the same number photons was proved.
The combination of the confocal scanning microscopy and the defocusing imaging in the plane of imaging system was proposed. A switch lens and a pinhole with fine focusing aid are used to switch between the confocal scanning imaging mode and defocusing imaging mode. Objectives of different magnification can be used to get different field of vision. The complementary images can offer more information than any single one. Image blur or distortion caused by scanning, such as the displacement of the target and the excursion of scanning stage, can be corrected according to the comparison of two images. Location and adjustment of the target can be achieved easily and the accuracy of scanning image will be improved obviously. Some samples were tested on a home-built system.
The two-photon absorption properties of a new dye have been experimentally studied using the comparable two-photon induced fluorescence method with a pulsed titanium-sapphire laser. This new dye has a two-photon absorption cross-section of 1.7 x 10-48 cm4s/photon at 790nm.
We combine the differential confocal microscopy and annular pupil filter together. The theory of differential confocal microscopy and the property of the annular pupil filter are discussed in detail. The results of computer simulation and experiment prove that this method can extend the axial dynamic range and improve transversal resolution of 3D profilometry at sacrificing axial resolution.
The pulse compression of two-cell SBS system in CCl4 liquid was experimentally investigated. The duration of Stokes pulse was tunable by simply changing the separation between two cells and the tuning range depended on the pump energy. By increasing the input energy, the wider tuning range of pulsewidth could be achieved. The near-diffraction limited output pulses have achieved and the shot to shot stability on far-field divergence angle was also measured. The numerical simulation on pulse shape of two-cell SBS system was made and agreed with the experimental results well.
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