Abstract

We recently introduced¹ a new class of femtosecond source which operates at ultraviolet wavelengths with 100-MHz repetition rate and milliwatt average power by intracavity frequency doubling of a passively mode-locked femtosecond dye laser. In sharp contrast to earlier studies of intracavity frequency doubling in synchronously pumped picosecond dye lasers,^2,3 which lacked a saturable loss medium, we achieved milliwatt UV output without perturbing the pulse duration, frequency bandwidth, power, or mode-locking stability of the fundamental laser output. We augment Haus’s model⁴ of a passively mode-locked laser with a frequency-doubling element to examine quantitatively the underlying physical mechanisms responsible for such favorable performance of frequency- doubled femtosecond sources. In particular, we show that saturable loss and gain medium can compensate the destabilizing and pulse broadening influence of an intracavity frequency doubler.

© 1988 Optical Society of America