GENERATION OF FEMTOSECOND LIGHT PULSES IN THE NEAR INFRARED AROUND X = 850 nm

The generation of light pulses around 100 fs was made possible by the introduction of the colliding pulse mode-locking technique [ 11. The specially designed laser produced femtosecond light pulses in the spectral range around 620 nm. The advanced understanding of the pulse shaping process and the introduction of an intracavity compensation of dispersion allowed the stable generation pulses between 27 fs and 100 fs [2-51. While the standard CPM laser operates with cw pumping by an argon ion laser, attempts have been made to synchronously pump CPM lasers. Recently we were able to show that by using a specially designed pumping scheme stable CPM laser action is possible with synchronous pumping [6]. This laser system was further advanced now generating 60 fs pulses at 625 nm [7]. The major draw-back of CPM dye lasers is the very narrow wavelength range. Up to now the emission of femtosecond lasers is restricted to wavelengths between 600 nm and 635 nm. Femtosecond light pulses at other wavelengths have been produced with complex and expensive systems after amplification of the red femtosecond pulses and subsequent continuum generation [8,9]. In this letter we report on the first operation of a femtosecond laser in a new wavelength range. The wavelength of the femtosecond pulses is located in the near infrared; the tunability extends from 840 to 880 nm. Stable pulse trains with pulse durations as short as 65 fs were achieved. The construction of the infrared femtosecond laser