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High harmonic generation (HHG) in solids results from an interplay between intraband acceleration and electron-hole recombination driven by a high-intensity laser pulse. Here, we theoretically reveal that the driving pulse duration can play…

Optics · Physics 2026-03-06 Alba de las Heras , Ofer Neufeld , Angel Rubio

Diffraction radiation (DR) is produced when a charged particle passes through an aperture or near a discontinuity in the media in which it is traveling. DR is closely related to transition radiation (TR), which is produced when a charged…

Accelerator Physics · Physics 2009-11-06 R. B. Fiorito , D. W. Rule

We develop a multipolar theory of second-harmonic generation (SHG) by dielectric nanoparticles made of noncentrosymmetric materials with bulk quadratic nonlinearity. We specifically analyze two regimes of optical excitation: illumination by…

In chiral sum frequency generation (C-SFG), the chiral nature of ${\chi}^{(2)}$ requires the three involved electric fields to be pairwise non-parallel, leading to the traditional non-collinear configuration which is a hindrance for…

Optics · Physics 2016-12-07 Ziheng Ji , Wentao Yu , Hong Yang , Kaihui Liu , Qihuang Gong , Zhiwen Liu , Kebin Shi

By sidestepping the intractable calculations of many-body wavefunctions, density functional theory (DFT) has revolutionized the prediction of ground states of materials. However, predicting nonlinear responses--critical for next-generation…

We report an approach for high-resolution spectroscopy using a widely tunable laser emitting in the molecular fingerprint region. The laser is based on difference-frequency generation (DFG) in a nonlinear orientation-patterned GaAs crystal.…

We theoretically investigate detuning-dependent properties of high-order harmonic generation (HHG) in monolayer transition metal dichalcogenides (TMDCs). In contrast to HHG in conventional materials, TMDCs show both parallel and…

Materials Science · Physics 2018-04-18 Tomohiro Tamaya , Satoru Konabe , Shiro Kawabata

We study the low-frequency properties of the bulk photovoltaic effect in topological semimetals. The bulk photovoltaic effect is a nonlinear optical effect that generates DC photocurrents under uniform irradiation, allowed by…

Mesoscale and Nanoscale Physics · Physics 2021-07-12 Junyeong Ahn , Guang-Yu Guo , Naoto Nagaosa

We report the first experimental observation of frequency shift in high order harmonic generation (HHG) from isotopic molecules H2 and D2 . It is found that harmonics generated from the isotopic molecules exhibit obvious spectral red shift…

Atomic Physics · Physics 2016-04-25 Lixin He , Pengfei Lan , Chunyang Zhai , Feng Wang , Wenjing Shi , Qingbin Zhang , Xiaosong Zhu , Peixiang Lu

One key parameter in the high-order harmonic generation (HHG) phenomenon is the exact frequency of the generated harmonic field. Its deviation from perfect harmonics of the laser frequency can be explained considering (i) the single-atom…

Classifier-free guidance (CFG) has become an essential component of modern conditional diffusion models. Although highly effective in practice, the underlying mechanisms by which CFG enhances quality, detail, and prompt alignment are not…

Machine Learning · Computer Science 2025-06-25 Seyedmorteza Sadat , Tobias Vontobel , Farnood Salehi , Romann M. Weber

Terahertz sources based on intra-cavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically-pumped semiconductor sources capable of operating at…

We present a 100 kHz broadband vibrational sum-frequency generation (VSFG) spectrometer operating in the 5.5-10.5 $\mu$m (950-1750 cm$^{-1}$) wavelength range. The mid-infrared beam of the system is obtained from a collinear, type-I…

Instrumentation and Detectors · Physics 2019-06-26 Zsuzsanna Heiner , Li Wang , Valentin Petrov , Mark Mero

Superfluorescence (SF) is the collective emission of intense, coherent light from an interacting ensemble of quantum emitters1-4. While SF has been observed in several solid-state materials5-8, the spontaneous generation of circularly…

The nonlinear optical properties and electro-optic effects of some oxygen-octahedric ferroelectrics are studied by the density functional theory (DFT) in the local density approximation (LDA) expressions based on first principle…

Materials Science · Physics 2011-12-30 Amirullah M. Mamedov , Ekmel Ozbay

We present a modeling of the nonlinear optical response of a metal surface in order to account for recent experimental results from two-color Sum-Frequency Generation experiments on gold. The model allows calculating the surface and bulk…

Chemical Physics · Physics 2019-05-16 Bertrand Busson , Laetitia Dalstein

We present a detailed analysis and comparison of dielectric waveguides made of CdTe, GaP, GaAs and InP for modal phase matched optical difference frequency generation (DFG) in the terahertz domain. From the form of the DFG equations, we…

Modifications on the predictions about the matter power spectrum based on the hypothesis of a tiny contribution from a degenerate Fermi gas (DFG) test-fluid to some dominant cosmological scenario are investigated. Reporting about the…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-19 E. L. D. Perico , Alex E. Bernardini

We study the conductance fluctuation in topological semimetals. Through statistic distribution of energy levels of topological semimetals, we determine the dominant parameters of universal conductance fluctuation (UCF), i.e., the number of…

Disordered Systems and Neural Networks · Physics 2017-10-25 Yayun Hu , Haiwen Liu , Hua Jiang , X. C. Xie

We study the Fermi surface contribution to the nonlinear DC photocurrent at quadratic order in a spatially uniform optical field in the ultra-clean limit. In addition to shift and injection current, we find that polarized light incident on…

Materials Science · Physics 2021-12-07 Lingyuan Gao , Zachariah Addison , E. J. Mele , Andrew M. Rappe