1047-6938/03/05/0046/6-$0015.00 © Optical Society of America A Quasiperiodic Approach to Ultrashort Pulses

To optically control atomic and molecular processes, the optical waveform must be shaped with as much precision as possible. Precise waveform shaping requires maximization of the number of phase-adjustable frequencies. In this article the authors describe a general technique to multiplicatively increase the number of generated frequencies by use of modulators in series. A quasiperiodic spectrum of collinear Raman sidebands is dispersed and projected on a screen. The beams are scattered as they pass through liquid nitrogen vapor. Many methods of generatingbroad spectra and short pulsesrely on modulation of a beam of laser light. In communications, modu-lation is a means of imprinting informa