Population
inversion dynamics in the few-cycle pulse limit
Nada Doslic, Ruder Boskovic Institute,
We shall discuss the population inversion in
a two-level system generated by sub-one-cycle pulse excitation. Specifically, the effect that the time derivative of the
pulse envelope has on the Rabi dynamics is explored. We find
a shortening of the Rabi inversion period and show that complete inversion is
unobtainable under resonant, ultrashort pulse
condition. The impact of non-resonant and carrier-envelope phase dependent effects
on the dynamics of two-level systems is studied numerically, and conditions for
complete population inversion are derived.
The second part of the talk focuses on
multi-level systems. We present a zero-net-force modification of the optimal control
algorithm which allows us to extend the algorithm into the ultrashort
pulse domain. By combining the analysis of the control landscapes and that of
optimal control theory, we were able to formulate a general mechanism suitable
for laser control by ultrashort pulses. The strategy
consists of a superposition of two π-pulses with carrier envelope phases
of φ = π/2. The first pulse is effectively in resonance with the
targeted transition, while the second one, fired
at around the minimum of the first pulse second lobe removes leaking to the
dipole-coupled background state. In order to compensate for the pulses ultrashort duration, the carrier frequencies of both pulses
are red-shifted from the spectroscopic resonance.