Ultrafast Dynamics of High-Harmonic Generation in Terms of Complex Floquet Spectral Analysis

Abstract

Abstract:We studied the high-harmonic generation (HHG) of a two-level-system (TLS) driven by an intense monochromatic phase-locked laser based on complex spectral analysis with the Floquet method. In contrast with phenomenological approaches, this analysis deals with the whole process as a coherent quantum process based on microscopic dynamics. We have obtained the time-frequency resolved spectrum of spontaneous HHG single-photon emission from an excited TLS driven by a laser field. Characteristic spectral features of the HHG, such as the plateau and cutoff, are reproduced by the present model. Because the emitted high-harmonic photon is represented as a superposition of different frequencies, the Fano profile appears in the long-time spectrum as a result of the quantum interference of the emitted photon. We reveal that the condition of the quantum interference depends on the initial phase of the driving laser field. We have also clarified that the change in spectral features from the short-time regime to the long-time regime is attributed to the interference between the interference from the Floquet resonance states and the dressed radiation field.

Floquet-theoretical formulation and analysis of high-order harmonic generation in solids

“…Third, we have treated the electric field classically. Quantum processes lead to spontaneous emission of photons [61], which is not discussed in the present work. These effects are all important and our simple model could serve as a starting point in interpreting the experimental data.…”

The Dynamical Casimir Effect in a Dissipative Optomechanical Cavity Interacting with Photonic Crystal

“…which is satisfied for the narrow photonic band and small external amplitude, we can restrict ourselves to {|a * , 1) , |a, 0) } space. Using the projection operators [52] of P ≡ |a * , 1) (a * , 1| + |a, 0) (a, 0| , Q ≡ 1 − P ,…”

Classical Radiation Damping and Emission of Optical Vertex as Microscopic Irreversible Process

“…It is known that we need a higher harmonic emission of light to have the optical vertex [2]. A good candidate to have the higher harmonics is the system with a time periodic external force that is treated in terms of the Froque Hamiltonian [13].…”

“…and so on, corresponding to the relation (6). These new dual modesQ 1 and Q cc 1 are obtained through the residue at the pole ω k = z 1 in the complex plane in the contour deformation of the integration in the Hamiltonian (13). The rest of the contour integral definesQ k and Q cc k .…”

“…As an application of this approach of the irreversible process based on the microscopic laws of physics, we have already found many interesting phenomena, mainly for quantum unstable systems where excited atoms decay due to effect of the resonance singularity that comes from a coupling with a photon field with a continuous spectrum [13][14][15][16][17][18].…”