The quest for the world's shortest laser pulse has led to a remarkable pace of development in ultrafast laser technology. Although pulses of only a few cycles duration have been made, clearly the observation of a 0-fs pulse would represent a key result in this field (see Fig. 1). In most experiments, a 100-fs pulse is amplified and passed through a nonlinear medium, generally a simple single-mode silica optical fiber. The resulting nonlinear propagation creates a large bandwidth increase, and, with careful control of subsequent optical phases, significant compression ratios have been obtained. A simple linear extrapolation predicted that continued progress should result in an important milestone (dashed line): the pulsewidth should have gone to zero in late 1986 and become negative in 1987. Incorporation of prisms have produced at best 6-fs (three-cycle) pulses.
by W.H. Knox, R.S. Knox, J.F. Hoose, and R.N. Zare