Hyper-Raman lines emission concomitant with high-order harmonic generation

Abstract

Hyper-Raman lines (HRL) resulting from strong-field light-matter interaction have been predicted theoretically in the 1990s but never identified in high-order harmonic generation experiments. Here, we use a combination of 800 and 400 nm laser pulses to control independently the two processes required for the hyper-Raman emission: creation of a coherence between two electronic states and laser-dressing of these states. As a result we observe simultaneously high-order harmonics, XUV free induction decay and HRL. We investigate experimentally and numerically the properties of this novel emission source. It can be of high interest, amongst others, for high-resolution spatio-temporal spectroscopy of excited electronic states in the same fashion high-order harmonics generation provides it for ground state.

New schemes for creating large optical Schrodinger cat states using strong laser fields

“…considering the quantum aspects of the atomic, molecular or solid-state system while keeping a classical behaviour for the laser field due to its high-photon number. Recent approaches have attempted to study these phenomena, theoretically [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] and experimentally [32][33][34], from a fully quantum-mechanical perspective, that is, considering the quantum nature of both the laser field and the atom. However, it was in Ref.…”

Role of Spin-Orbit Coupling in High-order Harmonic Generation Revealed by Super-Cycle Rydberg Trajectories

“…To confirm this picture, we model high-harmonic generation from an excited state using the two-level system (TLS) of Ref. [24]. The TLS is driven by the field E(x, t) = g(x)f (t)E 0 sin ωt, with E 0 = 0.08 a.u., ω = 0.056954 a.u.…”

“…and the dipole coupling between the ground and the excited states is set to d 10 = √ ∆/2ω = 6.57 a.u. to mimic the ponderomotive shift of the Rydberg state [24] and the associated intensity-dependent phase accumulated by the excited state. The time-dependent dipole moment at the position x is d(x, t) = d 10 Re[c 0 (t)c * 1 (t)], where c k (t) are found by solving the coupled equations…”

“…Our work sheds light on the role of Rydberg states in the HHG process. The influence of excited states in HHG has been the subject of many experimental [15,[24][25][26][27] and theoretical investigations [28][29][30]. On very short time-scales, the excitation of Rydberg states followed by ionization and recombination onto the ground state was shown to lead to a delayed (by few femtoseconds) emission of an attosecond pulse train [15].…”

“…On very short time-scales, the excitation of Rydberg states followed by ionization and recombination onto the ground state was shown to lead to a delayed (by few femtoseconds) emission of an attosecond pulse train [15]. On longer timescales, the population of Rydberg states can induces hyper-Raman lines [24,31] if a dressing laser field is added. Moreover, on timescales much longer than the laser pulse duration, the Rydberg wavepacket generates coherent XUV free-induction decay (FID) [26,32].…”