Two-photon fluorescence excitation with a microlens fabricated on the fused silica chip by femtosecond laser micromachining

We report on the fabrication of a microlens on a fused silica chip with excellent optical performance by femtosecond laser microfabrication. We show, both in theory and experimentally, that the fabricated microlens offers a high resolution approaching the optical diffraction limit. Moreover, two-photon excitation of fluorescence with the fabricated microlens is demonstrated. The lateral and axial resolutions of fluorescence are measured to be ∼1.7 and 12.3 μm, respectively.