Abstract

Non linear spectroscopy requires systems producing high peak power ultrashort pulses. Most of such femtosecond apparatus are based on an initial cavity producing low energy pulses which have to be further amplified in a dye medium pumped by a pulsed laser. Until very recently most of these systems delivered high peak power pulses with a spectrum centered around 620 nm. Two exceptions are noteworthy. One year ago W. Knox reported a system based on an infrared oscillator coupled to an amplifier pumped by a 6 kHz repetition rate copper vapor laser (CVL) [1]. The performances were 1 μJ energy per pulse after amplification and 120 is duration after compensation of the dispersion. The spectrum of emission centered at 805 nm was determined by the active-passively modelocked dye laser. Flexibility in tunability is however essential for time resolved spectroscopy. This is the reason why we have previously developed a method of production of tunable high peak power pulses in the femtosecond range through the amplification of the continuum [2]. Up to now this technique has been used in Nd-Yag pumped dye amplifiers and has allowed to generate pulses in the range of energy 1 to 100 μJ, of duration comprised between 150 and 300 fs in vatious regions of the spectrum.

© 1988 Optical Society of America