We use molecular deuterium and two driving lasers to demonstrate collinear generation of mutually coherent equidistant sidebands, covering $50000{\mathrm{cm}}^{\ensuremath{-}1}$ of spectral bandwidth and ranging from $2.94\ensuremath{\mu}\mathrm{m}$ to 195 nm in wavelength. The essential idea is the adiabatic preparation of a single, highly coherent ( $|{\ensuremath{\rho}}_{\mathrm{ab}}|\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.33$) molecular eigenstate.
We study the generation of subfemtosecond pulses with the molecular coherence control in stimulated Raman scattering. We show analytically that the antiphased state temporally advances the higher frequencies with respect to the lower frequencies during a beating cycle. After some propagation distance, due to the dispersion and the difference between the antiphased and phased states in advancing high or low frequencies, the coherence is highest on the negative side of the detuning, when the two-photon Rabi frequency is about equal to the detuning. This asymmetry of the coherence magnitude with respect to the negative and positive sides of the Raman detuning is reflected in the behavior of the tuning characteristics of the high-order frequency components. When the Raman detuning is small, although the process is nonadiabatic, the subfemtosecond pulse generation may occur for both negative and positive sides of the detuning.
We report an experimental observation of simultaneous rotational and vibrational collinear Raman generation in low pressure cooled deuterium gas, with only two narrow-band laser pulses applied at the input of the molecular cell. Only the fundamental vibrational transition
Q1 (0) is driven strongly in this experiment. However, in addition to efficient vibrational Raman generation we observe generation of a large number of rotational sidebands (more than 100) corresponding to
S0 (0) transition. We notice that fine-tuning of the frequency difference of the driving fields near the vibrational Raman resonance changes dramatically the aspects of the generated spectrum and the efficiency of rotational generation: from complete suppression of a self-starting stimulated rotational Raman generation to a strong enhancement of two orders of magnitude. We conduct a numerical analysis that allows us to attribute this behavior to quantum interference among the probability amplitudes of the three molecular states involved.