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.