Harmonic

Quantum mechanics

Linguistics

High harmonic generation

Philosophy

Computational physics

Operating system

Atomic physics

Reciprocal

Computer science

Classical mechanics

Physical chemistry

Polarization (electrochemistry)

Reciprocal lattice

Laser

Physics

Trajectory

Ionization

Amplitude

Mathematics

Geometry

Chemistry

Electron

Perspective (graphical)

Diffraction

Cutoff

Space (punctuation)

Physical Review Letters

We revisit the mechanism of high-harmonic generation (HHG) from solids by comparing HHG in laser fields with different ellipticities but a constant maximum amplitude. It is shown that the cutoff of HHG is strongly extended in a circularly polarized field. Moreover, the harmonic yield with large ellipticity is comparable to or even higher than that in the linearly polarized field. To understand the underlying physics, we develop a reciprocal-space-trajectory method, which explains HHG in solids by a trajectory ensemble from different ionization times and different initial states in the reciprocal space. We show that the cutoff extension is related to an additional preacceleration step prior to ionization, which has been overlooked in solids. By analyzing the trajectories and the time-frequency spectrogram, we show that the HHG in solids cannot be interpreted in terms of the classical recollision picture alone. Instead, the radiation should be described by the electron-hole interband polarization, which leads to the unusual ellipticity dependence. We propose a new four-step model to understand the mechanism of HHG in solids.

Reciprocal-Space-Trajectory Perspective on High-Harmonic Generation in Solids