Non-Adiabatic Dressed States for a Quantum System Interacting With Light Pulses

Li Yongfang

In the dressed state picture,the transition process and the time evolution dynamic process of a two-level system excited by the sinusoidal phase-modulated shaping pulse are investigated with the Bloch vector sphere schematic diagram.The results show that when a two-level system is interacted with the proper sinusoidal phase shaping pulse,the population is inversed and remained in same state and is irrelevant of the!shaping pulse.During the interaction between field and system,the adiabatic states of particles are variant with the different circumstances of light field phase under the adiabatic condition.

G. Compagno, Roberto Passante, Franco Persico

Ivan Georgiev Koprinkov

We introduce non-adiabatic semiclassical dressed states for a quantum system interacting with an electromagnetic field of variable amplitude and phase, in the presence of dumping. We also introduce a generalized adiabatic condition that allows one to find a closed-form solution for the dressed states. The influence of non-adiabatic factors on the dressed states due to the amplitude and phase field variations and dumping has been found.

Loïc Joubert-Doriol

Artur Mikhailovich Ishkhanyan, M. Hakobyan

Fabian Cipura

In this work, we thoroughly investigated frequency conversion towards ultrashort picosecond (ps) laser pulses in the vacuum ultraviolet (VUV) spectral regime via nonlinear optics in coherently-driven quantum systems at high intensities. We applied approaches of adiabatic quantum dynamics relying on coherent light-matter interactions, which modify the "bare" eigenstates of a quantum system to "dressed" states and exploit slow (i.e., adiabatic) population evolutions via such dressed states. This enables enhancement of typically low-order, low-intensity nonlinear optics (at MW/cm², GW/cm²), where the light field perturbs the atomic level structure only weakly. On the other hand, aiming at nonlinear optics at higher orders, e.g., high-harmonic generation, strong light fields are applied (100 TW/cm², PW/cm²), which modify the Coulomb potential of the atom strongly. In this case, resonances play no role anymore and adiabatic quantum dynamics via atomic resonances will not work. With this work, we demonstrated the implementation of adiabatic quantum dynamics and coherently prepared media for nonlinear optics in an intermediate intensity regime (TW/cm²), i.e., at Keldysh parameters approaching γ≈1. The fundamental question was, whether the high intensities still permit us to drive and exploit coherent-adiabatic dynamics via dressed states for enhancement of frequency conversion processes. We investigated two approaches to enhance the frequency conversion yield applying nonlinear optics in coherently-driven quantum systems (rare gases). In the first approach, we resonantly enhanced harmonic generation via dressed states with large Autler-Townes splittings. With this approach, we demonstrated how to make atomic resonances available for an initially far detuned fixed-frequency pump laser and showed a compensation for inevitable, perturbing Stark shifts. In the second approach, we investigated frequency conversion, enhanced by coherent population return (CPR) and preparation of maximal atomic coherences at high intensities. With this approach, we showed how to maximally benefit from an atomic resonance via adiabatically driven frequency conversion, i.e., by detuning the strong pump laser slightly from the resonance.