Tunable, low-repetition-rate, cost-efficient femtosecond Ti:sapphire laser for nonlinear microscopy
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We report on a broadly tunable, long-cavity Ti:sapphire laser oscillator being mode-locked in the net negative intracavity dispersion regime by Kerr-lens mode-locking, delivering τ FWHM<300 fs pulses at 22 MHz repetition rate. The wavelength of the laser can be tuned over a 170 nm wide range between 712 nm and 882 nm. Having a typical pump power of 2.6 W, the maximum pulse peak power is 60 kW. Comparison of the reported laser with a standard, 76 MHz Ti:sapphire oscillator regarding two-photon excitation efficiency in a laser scanning microscope shows that the 22 MHz laser generates the same fluorescence signal at considerably, 1.82 times lower average power, which is expected to result in a reduced photothermal damage probability of biological samples. This fact along with the broad tunability and a low pump power requirement makes this cost-effective laser an ideal light source for nonlinear microscopy.
KeywordsPump Power Output Coupler Excitation Power Fluorescence Lifetime Imaging Microscopy Input Coupler
We gratefully acknowledge the fruitful discussions with Attila Kolonics on biological issues related to nonlinear microscopy. We also thank Attila Szigligeti and Dóra Haluszka for their technical assistance. This research was supported by the Hungarian Development Agency (NFÜ) under contract no. TECH-09-A2-2009-0134 and by R&D Ultrafast Lasers Ltd. under contract no. BAROSS-KM07-KM-TERM-07-2008-0003.
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