Abstract

We present a highly versatile confocal microscopy setup based on a single mode-locked erbium-doped fiber laser. This system provides ultrashort pulses for nonlinear microscopy at 1550 nm (fundamental), from 1050 nm to 1400 nm (tailored supercontinuum) and at 775 nm (second harmonic). Pulse durations in the focal plane are 200 fs at 775 nm and less than 40 fs for the tunable infrared. Instead of using a photonic crystal fiber (PCF), a low-noise supercontinuum is generated in a conventional single-mode fiber. This technique allows light coupling via fusion-spliced standard free-space couplers and results in robust operation with minimum acoustic pickup. Therefore, highly stable visible pulses tunable from 520 mn to 700 mn are available via frequency doubling. This radiation allows to precisely address fluorophores absorbing in the green to near-infrared region by linear confocal microscopy. Secondly, multiphoton techniques may be performed, including targeted photomanipulations. In order to characterize the system, we have investigated pulse broadening after propagation through the microscope. The temporal pulse durations in the focus are 90 fs at 1.55 pm, less than 50 fs between 1080-1400 mn, and below 300 fs at 780 mn. We present two-photon fluorescence microscopy of pyramidal neurons expressing dTomato excited at 1070 mn. Also, we induce spatially localized cyclobutane-pyrimidine dimers (CPDs) in DNA via three-photon absorption [1],

© 2007 IEEE