OPTICAL SATURATION MEASUREMENTS OF FLUOROPHORES IN SOLUTION WITH PULSED FEMTOSECOND EXCITATION AND 2-DIMENSIONAL CCD CAMERA DETECTION

We present a new method for the measurement of saturation of the optic al transition of fluorescent molecules in solution, which is based on detection with a CCD camera of a two-dimensional projection of the thr ee-dimensional, spatially nonuniform fluorescence intensity distributi on as generated in a bulk solution of the fluorophore by excitation wi th focused femtosecond optical pulses. Essential to the method is (a) a combination of information from a measurement in saturation and one not in saturation and (b) for the measurement in saturation, the simul taneous observation of both saturated and nonsaturated regions of the fluorescence intensity distribution. The experimental setup is straigh tforward and good agreement is found between the theory and the experi mental data. (C) 1997 Optical Society of America.