Abstract

One of the most important proposed methods to generate subfemtosecond (sub-fs) pulses is the so-called high-order stimulated Raman scattering by molecular modulation with two sufficiently intense single-mode laser beams, which has already been extensively studied [1]. The disadvantage of the above technique is that the pulse spacing of the generated sub-fs pulses is limited by the selected Raman transition. However, large and controllable pulse spacing is desirable for the development of high-intensity ultrafast laser techniques. In this report, we show that the pulse spacing can be enlarged in a controllable way with two phase-locked pairs of quasi-cw lasers whose carrier frequencies shift relatively to each other by Δω. The initial phase-locking of the driving laser pairs may be achieved by nonlinear frequency-mixing

© 2003 Optical Society of America