Diffraction of ultrashort optical pulses from circularly symmetric binary phase gratings.

The complete spatiotemporal characterization of the diffracted field of ultrashort pulses after passing through circularly symmetric binary phase diffraction gratings is carried out. The complex field is registered at different planes behind the gratings with an ultrashort-pulse measurement technique called SEA TADPOLE. Numerical simulations based on scalar diffraction theory are compared with the measurements.

Separation of the rotational contribution in fluorescence correlation experiments.

The theory of fluorescence correlation spectroscopy is reexamined with the aim of separating the contribution of rotational diffusion. Under constant excitation, fluorescence correlation experiments are characterized by three polarizations: one of the incident beam and two of the two photon detectors. A set of experiments of different polarizations is proposed for study. From the results of the experiments the isotropic factor of the fluorescence intensity correlation functions can be determined, which is independent of the rotational motion of the sample molecule. This function can be used to represent each fluorescence intensity correlation function as the product of the isotropic and the rotational factors. The theory is illustrated by an experiment in which rotational diffusion of porcine pancreatic lipase labeled with Texas Red was observed Texas Red is a label that allows precise fluorescence correlation experiments even in the nanosecond time range.

Fluorescence correlation spectroscopy in the nanosecond time range: rotational diffusion of bovine carbonic anhydrase B.

A fluorescence correlation experiment for measurement of rotational diffusion in the nanosecond time scale is described. Using this method, the rotational diffusion coefficient of bovine carbonic anhydrase B labelled with tetramethylrhodamine isothiocyanate was estimated to be Dr = (1.14 +/- 0.15) X 10(7) s-1 at 22 degrees C. The experiment is based on a cw argon ion laser, a microfluorometer with local solution flow inside the sample cell, and two photon detectors. The fluorescence intensity autocorrelation function in the nanosecond time range is computed with the help of a time-to-amplitude converter and a multichannel pulse-amplitude analyser.