All-linear control of attosecond pulse generation

We discuss a new approach to the controllable synthesis of fs- and sub-fs pulses which is based on the technique of ultrafast modulation of a laser field phase by impulsively prepared molecular vibrational (or rotational) motion with subsequent temporal compression. In this scheme, all the nonlinear effects involved in the medium preparation (molecule excitation, nonlinear self-action, ionization, etc.) are confined only within the pumping process, and the resulting spectral broadening of a relatively weak delayed (injection) pulse is linear in the field and therefore completely controllable. We show that combination of the technique of ultrafast molecular modulation with the methods of optical field phase-amplitude shaping (using prisms, gratings, etc.) allows direct controlling the period of generated trains of fs-pulses as well as duration in a single compressed fs-pulse. Basing on the results of analytical and numerical study of the combined system "phase-amplitude shaper + ultrafast molecular modulator + compressor", we discuss the potential of the approach for the controllable attosecond pulse generation. (C) 2002 Elsevier Science B.V. All rights reserved.