Effect of pulse phase and shape on the efficiency of multiphoton processes: Implications for fluorescence microscopy

Summary form only given. To date, the primary laser variables in ultrashort pulse excitation microscopy which are used to optimize efficiency have been wavelength, average power and peak power. In this paper we introduce two more parameters: pulse shape and phase (or chirp). Recently, we introduced a new technique for explicitly measuring the pulse shape and phase at the focus of a high numerical aperture system such as those used in microscopy. This will be critical in determining the optimal conditions which allow useful imaging, and minimal biological damage. Efficiency in fluorescence emission produced under ultrashort pulse laser excitation can be important for several reasons. Providing the most efficient excitation not only minimizes the amount of exposure which is required to render a scientifically viable image, but also any damage to the specimen which might occur as a result of this exposure. Thus, the time period over which biological systems could be viewed is maximized.