High-Efficiency Temporally Decorrelated Multifocal Arrays for Multiphoton Microscopy and Micromachining

摘要

Temporally decorrelated multifocal arrays eliminate the spatial interference of adjacent foci that occurs in multifocal arrays and allow multifocal imaging with the diffraction-limited resolution of a single focus even with closely spaced foci. To date, we have produced 1-D temporally decorrelated multifocal arrays using low throughput etalons, which limited the efficiency of the arrays. In this work, we demonstrate a 2-D high-efficiency cascaded-beamsplitter array for producing the beamlets. Using the cascaded beamsplitters, we split the 800-nm light from an ultrashort-pulsed Ti:Al_2O_3 laser into a 2-D array of beamlets in which the pulses arrive at a plane perpendicular to the propagation direction at different times. We then overlap the collimated beams with slightly different angles at the entrance aperture to a 1.25 NA oil-immersion objective and produce 2-dimensional array of foci that are temporally decorrelated. This allows multiphoton imaging with diffraction-limited focusing, even for pulses as short as 20-fs. This new method of imaging will make it possible to completely overlap the foci and eliminate the need for scanning. This makes highly efficient use of the power available from typical ultrafast lasers, increasing the frame rate in multiphoton microscopy and the throughput in micromachining applications.