arXiv subjects

Qing-Guo Fan

Publications and source records attributed to Qing-Guo Fan.

3 recordsLinked to original sources

arXiv2025

Enhancing Cutoff Energy of Solid High-Harmonic Generation from Bonding Length Perspective

High-harmonic generation (HHG) from solid state offers promising potential for attosecond optics with enhanced efficiency and compact configurations. However, Current implementations face critical limitations imposed by material damage thresholds, directly restricting spectral cutoff energies in nonperturbative regime. In this study, we control the cutoff energy through tailoring the bond length of materials, which is available by experimental strain. Employing real-time time-dependent density theory (rt-TDDFT) simulations, we find that the cutoff energy increases by nearly one third under a bond length compression of 7.5%. Our results reveal that it originates the band gap widening inducing the enhancement of interband cutoff energy, which is material-independent. This work provides novel theoretical insights for optimizing extreme ultraviolet sources, advancing potential applications in attosecond physics.

physics.optics↗

arXiv2025

Occupation-Driven emission asynchronous as a Fundamental Constraint on Solid-State Attosecond Pulses

A newly analytic occupation-resolved theory capturing the temporal structure of attosecond pulses (APs) is derived. We validate it with real-time time-dependent density functional theory and show remarkable temporal confinement of APs with laser intensity in solid state. Using a simplified field-driven electron excitation together with a generalized pre-acceleration picture, the interband emission timing demonstrate intrinsically temporal mismatched with field-synchronous intraband radiation, leading to a nonmonotonic dependence of attosecond pulse width on laser intensity. Our findings not only shed light on the microscopic mechanisms behind solid-state high harmonic generation (HHG), but also establish the fundamental time-domain constraint on solid-state APs independent of material damage thresholds.

physics.optics↗

arXiv2025

Revealing Material-Dependent Bicircular High-Order Harmonic Generation in 2D Semiconductors via Real-Space Trajectories

Solid-state high-order harmonic generation (HHG) presents unique features different from gases.Whereas the gaseous harmonics driven by counter-rotating bicircular (CRB) pulse universally peak at a "magic" field ratio approximately E_2{\omega}:E_{\omega}=1.5:1, crystals exhibit significant material-dependent responses. In monolayer MoS2, the harmonic yield experiences two maxima at the gas-like 1.5:1 ratio, and again in the single-color limit, whereas monolayer hBN shows a monotonic increase as the 2{\omega} component dominates. Combining time-dependent density-functional theory (TDDFT) and a minimal real-space trajectory analysis, we show that these differences arise from the interplay of Bloch velocity and anomalous Hall velocity. The trajectory model quantitatively reproduces the ab-initio results, and offers an intuitive prediction of the harmonics yield without further heavy computation. These insights provide practical guidance for tailoring solid-state HHG and for selecting 2D compounds with desirable responses.

physics.optics↗