Abstract

Today’s ultrafast all-solid-state lasers continue to demonstrate unsurpassed performances in terms of pulse duration, pulse repetition rates, average power and wavelength range: Optical pulses in the 5-femtosecond range are produced by a variety of methods [1]. Although different in technical detail, each method relies on the same three key components: spectral broadening due to the nonlinear optical Kerr effect, dispersion control, and ultrabroadband amplification. Pulses as short as 58 fs have been generated directly from a Ti:sapphire laser without any external pulse compression [2], [3]. The shortest pulses generated to date all rely on chirped mirrors [4] for dispersion compensation. A major limitation in chirped mirror design arises due to interference between light reflected at different penetration depths inside the mirror structure. This results in residual oscillations in the group delay dispersion (GDD) which ultimately limits pulse shortening. Unfortunately, there is always a trade-off between GDD-oscillations and reflection bandwidth. The double-chirped mirror technique (DCM, [5]) reduced GDD oscillations and resulted in the sub-6-fs pulses. Novel DCM designs result in a sufficiently large reflection bandwith that could, in principle, support 4-fs pulses.

© 2000 IEEE