Clean Pulse Technology

Multi-photon microscopy is a nonlinear microscopy technique where multiple near-infrared photons interact with the sample to create a fluorescent excited state. Thus, the fluorescence brightness and contrast when imaging depend on the peak-power of the excitation laser. The peak-power is determined by the average laser power, the repetition rate, the pulse duration at the sample plane and most importantly the temporal pulse quality.

Hence, with laser power and repetition rate fixed by experimental requirements, pulse duration and temporal pulse quality are the crucial factors that can be optimized for fluorescence image quality. Pedestals and side-wings on the temporal pulse profile do not contribute to the non-linear absorption but only unnecessarily heat the sample. Likewise, shorter pulses yield higher fluorescence intensity due to higher peak power. Thus, the combination of a high temporal pulse quality (a “clean pulse”) and a short pulse duration at the sample plane gives the best result in terms of overall 2-photon excitation. This ultimately improves the contrast and brightness of fluorescence images.