Abstract

We describe a multistage, copper vapor laser pumped, high repetition rate amplifier for femtosecond optical pulses using a compact design. Increased efficiency compared with earlier designs allows two dye cell stages to be pumped by a single copper vapor laser. The pump beam is delivered to antireflection coated cells¹ via multimode optical fiber. Small signal single pass gains of 20 are achieved. Using three passes in each stage, 70-fs pulses from a colliding pulse mode-locked dye laser are amplified to >20 µj at 8-kHz repetition rate. The output from the first stage of the amplifier may also be used to generate a white light continuum from which different wavelengths can be selected and amplified in the second stage, thus providing a tunable femtosecond source.² Alternately a single-mode fiber may be used between the stages for chirped pulse amplification. Dispersion is compensated after the second stage with prisms. This permits the generation of high intensity compressed femtosecond optical pulses.³ A modular design which cascades gain and nonlinearity provides a versatile and compact system that can be used for a wide range of femtosecond time-resolved spectroscopic studies.

© 1989 Optical Society of America