Single-Cycle Optical Pulses Synchronized with Molecular Oscillations

We have previously shown that coherent molecular motion can result in light modulation and subfemtosecond pulse compression. Our technique is based on adiabatic preparation of a macroscopic molecular ensemble in a single vibrational superposition-state [1]. Recently we have demonstrated collinear generation of mutually-coherent spectral sidebands, extending from infrared to far ultraviolet. We adjusted individual spectral phases to allow synthesis of desired single-cycle waveforms at the target, and characterized these waveforms by measuring the pulse-shape dependent multiphoton ionization rate (this work was done at Stanford University in Steve Harris's group) [2].

This Raman source can be used to study multiphoton processes in a regime not accessible by other light sources. In particular, it will allow measure-ment of ionization and high-order harmonic generation as a function of sub-cycle phase (or the phase of the carrier with respect to the pulse envelope). Moreover, by utilizing an even wider spectrum, this source will produce waveforms with a prescribed non-sinusoidal sub-cycle field shape.

By the very nature of the generation process, our light source produces trains of pulses, which are perfectly synchronized with the molecular motion in the given molecular system, and provide a unique tool for studying mole-cular and electronic dynamics. We envision producing a coherent molecular oscillation, applying a tightly focused train of perfectly timed pulses, adju-sting the delay, and studying electronic properties as function of molecular coordinates. We can use the coherent molecular motion to control multi-photon excitations in an EIT-like manner: We can have a destructive or a constructive interference among different multiphoton paths, depending on the relative phase of the molecular motion and the Raman sidebands. Possible extensions of this general technique range from studying compli-cated multi-mode motion of complex molecules, to probing ultrafast electro-nic dynamics in atoms.

REFERENCES:

1. S. E. Harris and A. V. Sokolov, Phys. Rev. A 55, R4019 (1997); Phys. Rev. Lett. 81, 2894 (1998); A. V. Sokolov, D. D. Yavuz, and S. E. Harris, Opt. Lett. 24, 557-559 (1999); A. V. Sokolov, Opt. Lett. 24, 1248 (1999).

2. A. V. Sokolov, D. R. Walker, D. D. Yavuz, G. Y. Yin, and S. E. Harris, Phys. Rev. Lett. 85, 562 (2000); Phys. Rev. A 63, 051801 (2001); Phys. Rev. Lett. 87, 033402 (2001).