Several different schemes for detecting ultrafast optical events are available. Streak cameras and schemes utilizing photomultipliers tubes (PMTs), such as time-correlated photon counting, pump-probe, up-conversion, phase- modulation, are found in most ultrafast labs. The selection of which method depends on several parameters of the event; such as the amount of collectable photons, wavelength, repeatability, the duration of the phenomena of interest, total duration of the event, available lasers used to initiate the event, and available budget. Streak cameras offer the most direct means of detecting ultrafast phenomena, with single photon sensitivity and time resolution down to 200-femtosecond. PMT schemes can offer a more cost-effective solution, depending on the above mentioned parameters and desired performance level. A newly developed NIR photomultiplier makes it possible to detect weak optical signals out to 1500 nm. This paper will discuss the tradeoffs between the various detection methods as well as cover a few illustrative applications.
A new picosecond time-resolved fluorescence microscope (PFM) has been developed for measuring and mapping the lifetime of laser excited fluorescence from a sample placed under a micro— scope. A compact laser diode is used to generate excitation pulses. The combination of a spectrograph and a streak camera performs time resolved fluorescence spectroscopy with a resolution of 40 ps ( 5 ps with deconvolusion). The lifetime and the intensity of laser excited fluorescence are analyzed b a computer and are displayed on a monitor as either a lifetime or intensity map.