Nonlinear Microscopy   GHz femtosecond lasers for nonlinear microscopy GIGAOPTICS' femtosecond lasers are successfully used for two-photon fluorescence microscopy as well as for second-harmonic-generation microscopy [1,2]. The main benefit of a 1GHz repetition rate laser instead of conventional 100 MHz systems is that lower pulse energies can be applied to the samples, leading to a significant reduction of dye bleaching and/or photodamage. The image quality remains the same or even improves because at the same time higher average powers can be applied and more pulses contribute to the average photomultiplier signals. On the right (Fig. 1), images of a patch-clamped living CA3 pyramidal neuron (mouse hippocampus) situated deep in a living organotypic brain slice culture are shown, recorded under illumination with a GIGAJET 20c at 805 nm wavelength. The 30 frames have been taken over the course of 2 hours under continuous illumination of the cell. Each of the 30 frames is a z-projection of 85 individual optical slices. Left and right panel correspond to the Fluo-5F (Ca²+-indicator) and Alexa-594 (morphology) channels. Click on the image to view the movie. The first real-time nonlinear microscope has been realized with a Gigaoptics GIGAJET 30, showing significantly reduced photodamage on living cells compared to a standard 80 MHz laser [2]. Benefits of using Gigahertz repetition rate lasers GIGAOPTICS' femtosecond lasers offer the following benefits to scientists in the field of nonlinear microscopy: • Compared to conventional 100 MHz laser systems, at 1GHz repetition rate, higher average powers can be applied to a living sample specimen while the pulse energy/peak intensity is kept low. This helps to significantly reduce photoinduced bleaching and photodamage. At the same time, the image quality remains the same or even improves because more pulses contribute to the average photomultiplier signals. • With a laser head footprint of 45×21 cm2, GIGAOPTICS’ turnkey 1 GHz femtosecond laser TACCOR exhibits an unparalleled compactness, saving precious laboratory space. References [1] A. Ehlers et al., "High (1 GHz) repetition rate compact femtosecond laser: A powerful multiphoton tool for nanomedicine and nanobiotechnology", J. Appl. Phys. 102, 014701 (2007). [2] S.-W. Chu et al., “Real-time second-harmonic-generation microscopy based on a 2-GHz repetition rate Ti:sapphire laser”, Opt. Expr. 11, 933 (2003).	Fig. 1: Images of a living CA3 pyra- midal neuron (mouse) recorded under illumination with a GIGAJET 20c at 805 nm wavelength. The 30 frames have been taken over the course of 2 hours. Click on the image to view the movie (2.83MB). Data courtesy of Dr. Alexander Drakew, Institute of Anatomy and Cell Biology, Department of Neuro- anatomy, University of Freiburg, Germany.