Pulse-picking multimodal nonlinear optical microscopy (Conference Presentation)

Abstract

We developed a pulse-picking multimodal nonlinear optical microscope that increases the sensitivity of label-free chemical imaging at low average laser power. Using a function-generator-controlled acousto-optic modulator, we collinearly combine two excitation wavelengths and can flexibly control the number of pulses at each pixel. The pulse-picking method gives over 1000x signal improvement for CARS and 20x for two-photon excitation fluorescent and second-harmonic generation at the same low average power. By varying the peak and average power of laser pulses, we evaluated the laser phototoxicity and found the optimal power window with the best sensitivity and minimum phototoxicity for tissue samples and live cells.