Pulse picking apparatuses and methods for nonlinear optical microscopy

A method for obtaining an image of a tissue sample, comprising:

• generating two or more laser beams at different frequencies;
• shifting the polarization direction of the two or more laser beams;
• delaying at least one of the two or more laser beams;
• merging the two or more laser beams into a spatially overlapped laser beam;
• modulating the spatially combined laser beam at different frequencies;
• focusing the modulated laser beam onto a sample;
• and
• obtaining an image from the sample after said focusing;
• wherein said generating produces two or more pulsed laser beams with a femtosecond pulse rate, the method further comprising:
• chirping the spatially overlapped laser beam to a spatially overlapped laser beam with a picosecond pulse rate.

A pulse picking multimodal nonlinear optical microscope, comprising:

• one or more lasers configured to generate two or more laser beams;
• a dichroic mirror configured to receive and combine the two or more laser beams into a combined laser beam;
• an acousto-optic modulator configured to receive the combined laser beam, modulate the combined laser beam at different frequencies, and output a modulated laser beam;
• and
• a microscope configured to receive the modulated laser beam from the acousto-optic modulator and focus the modulated laser beam onto a sample;
• wherein the combined laser beam is applied to the acousto-optic modulator at the Bragg angle error condition and the microscope collinearly combines the resulting spatially overlapped pump and Stokes beams at the first order diffraction of the acousto-optic modulator.