Analysis of fast axial scanning scheme using temporal focusing with acousto-optic deflectors

Abstract

Multiphoton microscopy has gained broad application in biology and medicine in the recent decade by assessing biological structure and function with high spatial resolution. Recently it has achieved fast two-dimensional x–y imaging by using inertia-free scanning mechanisms. However, the axial scanning speed is severely limited by mechanical inertia. This paper proposes a fast axial scanning scheme using temporal focusing implemented with an inertia-free scanning device, such as an acousto-optic device (AOD), and presents an experimental demonstration of two-photon axial scanning over a 9 µm range using AODs operated from 80 to 120 MHz. A theoretical analysis provides the detailed characteristics of this method. The effects of both the ratio of collimating lens to objective lens focal lengths or magnification (M), and the degree of group delay dispersion (GDD) in the light source on the temporal focusing and axial scanning range are described by theory and experiments.

Keywords:

• medical and biological imaging
• three-dimensional microscopy
• ultrafast lasers

Acknowledgments

The authors would like to thank Steven L. Jacques for helpful discussions and language revision. The work was supported by NSFC Grants 60278017 and 30328014.