3-DIMENSIONAL IMAGE-FORMATION IN CONFOCAL MICROSCOPY UNDER ULTRA-SHORT-LASER-PULSE ILLUMINATION

Reported in this paper is, to our knowledge, the first theoretical investigation of three-dimensional (3D) imaging properties in a confocal microscope under ultra-short-pulse illumination. Time-resolved, time-averaged and interferometric imaging modes in reflection and transmission systems are considered. The concept of the 3D transfer function is used to understand the imaging performance of the system. In the case of a 10 fs pulse, the spatial frequency bandwidth in the axial direction is twice that for a system under continuous-wave (CW) illumination, while the spatial frequency bandwidth in the transverse direction is increased by only 10%. As a result, axial resolution can be improved by approximately 30%, compared with the limiting value under CW laser illumination of the same wavelength as the pulsed beam.