Nonlinear optical microscopy based on double-clad photonic crystal fibers.

We report on a nonlinear optical microscope that adopts double-clad photonic crystal fibers for single-mode illumination delivery and multimode signal collection. It is demonstrated that two-photon fluorescence and second harmonic generation signals can be simultaneously collected in such a microscope with axial resolution of 2.8 microm and 2.5 mum, respectively. The delivery and detection efficiencies of the photonic-crystal-fiber- based microscope are significantly improved by approximately 3 times and 40 times compared with those in the single-mode fiber-optic microscope. The high resolution three-dimensional second harmonic generation images from rat tail tendon demonstrate the effectiveness of the system.