Three-photon absorption materials and applications

We have demonstrated efficient three-photon excitation in a number of nonlinear organic materials developed at our center or in cooperation with other research groups. The three-photon absorption (3PA) properties of these materials are studied using a femtosecond Ti:sapphire oscillator-amplifier laser system associated with an optical-parametric amplifier. Considering the transverse intensity distribution of the incident beam during measurements, the 3PA induced nonlinear transmission of the incident beam with a Gaussian transverse spatial profile is derived. Some of the 3PA-active materials are highly fluorescent while some others are nonfluorescent. In one of these materials, vibrational resonance enhanced broadband multiphoton absorption was founded. These materials can be used in optical power limiting and stabilization, frequency- upconversion imaging and microscopy etc. Some recent experiments of three-photon pumped power limiting and stabilization are briefly presented.