Possibility of coherent excitation of molecular vibrations in a resonance light field

Alex C. Han

Wave-mechanical phenomena such as resonance and interference, in both light and matter, are central to the principles of quantum coherent control over molecular processes. Focusing on the dynamical aspects, this dissertation is a compilation of studies on the interaction physics involving wave packets in molecules, the driving light field, and the underlying coherence and control. In each work, we will demonstrate interesting correlations between the properties of a carefully designed excitation light field and desirable outcomes of the molecules quantum dynamics. We will analyze the dynamical effect of a Feshbach resonance in the adiabatic Raman photoassociation for ultracold diatomic molecule formation from ultracold atoms. A narrow resonance is shown to be able to increase the effective number of collisions, in an ultracold atomic gas, that are available for photoassociation. This results in an optimal resonance width much smaller than the atomic collision energy bandwidth, due to the balance between the effective collision rate and single-collision transfer probability. Next, we demonstrate the linear molecular response to high-intensity, broadband, shaped optical fields. We show that this originates from interferences based on intra-pulse Raman excitations, and thus response linearity is not unique to the first-order perturbative limit and can not be used to infer the strength of the field. In the last study, we simulate the stochastic vibrational wave packet and dissociation-flux dynamics in a molecule excited by light with temporal and spectral incoherent properties. Between this case and that using a coherent pulse with the same spectral profile, we compare the vibrational wave functions and the loss of electronic and vibrational coherence, and demonstrate the qualitative difference between coherently and incoherently driven dynamics in molecules.

E. Garmire, F. Pandarese, Charles Hard Townes

Yu. T. Mazurenko, Vladimir Sergeevich Yarunin

Pooja Nadkarni Singh, Anil K. Patnaik, Sukesh Roy +2 more

We have considered the Raman scattering in molecular media. Applying two laser fields in a two-photon resonance with vibrational transition, we have studied the role of rotational levels for excitation of vibrational coherence. It is shown that the molecular vibrational coherence strongly depends on the effect of coherent population trapping for rotational levels. The obtained results are important for applications of Raman spectroscopy to molecular detection in engineering, chemical, and biological applications.

Yuri V. Rostovtsev, Zoe‐Elizabeth Sariyanni, Marlan O. Scully

We demonstrate a strong coherent backward wave oscillation using forward propagating fields only. This is achieved by applying laser fields to an ultra-dispersive medium with proper chosen detunings and an appropriate spatial phase to excite a molecular vibrational coherence that corresponds to a backward propagating wave. This leads to new possibilities of controling phase-matching direction as well as having phase-matching simultaneously in forward and backward directions. It has applications to generation of entangled photon state.

Alexander A. Ivanov, V. V. Parail, T. K. Soboleva