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We study the non-Gaussianity and secondary Gravitational Waves (GWs) in the process of the Primordial Black Holes (PBHs) production from inflation. In our work, we focus on the $\alpha$-attractor inflation model in which a tiny bump in the…

General Relativity and Quantum Cosmology · Physics 2022-08-31 Kazem Rezazadeh , Zeinab Teimoori , Saeid Karimi , Kayoomars Karami

We investigate the non-Gaussianity of second-order matter density perturbations induced by primordial gravitational waves (GWs). These tensor-induced scalar modes arise from local fluctuations in the GWs energy density, which is quadratic…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-12 Mariam Abdelaziz , Pritha Bari , Sabino Matarrese , Angelo Ricciardone

High-order harmonic generation (HHG) is investigated for H$_2^+$ and its isotopomers under seven- and ten-cycle trapezoidal laser pulses at 800 nm wavelength and $I$=4$\times 10^{14}$ W$/$cm$^2$ intensity. We solved numerically…

Atomic Physics · Physics 2016-03-03 H. Ahmadi , M. Vafaee , A. Maghari

We experimentally demonstrate shaping of the two-photon wavefunction of entangled photon-pairs, utilizing coherent pulse-shaping techniques. By performing spectral-phase manipulations we tailor the two-photon wavefunction exactly like a…

Quantum Physics · Physics 2011-12-06 Avi pe'er , Barak Dayan , Asher A. Friesem , Yaron Silberberg

By combining analytical and numerical approaches, we study resonantly enhanced second-harmonic generation (SHG) by individual high-index dielectric nanoparticles made of centrosymmetric materials. Considering both bulk and surface…

Optics · Physics 2018-01-08 Daria Smirnova , Alexander I. Smirnov , Yuri S. Kivshar

We present a model for quasi-phase matching (QPM) in high-order harmonic generation (HHG). Using a one-dimensional description, we analyze the time-dependent, ultrafast wave-vector balance to calculate the on-axis harmonic output versus…

We designed, fabricated and tested gallium phosphide (GaP) nano-waveguides for second harmonic generation (SHG). We demonstrate SHG in the visible range around 655 nm using low power continuous-wave pump in the optical communication O-band.…

We theoretically investigate high-order harmonic generation (HHG) and its ellipticity in gapped graphene, driven by a femtosecond short-pulse laser at various orientation angles, employing the two-band density-matrix equations within the…

Atomic Physics · Physics 2025-05-21 Xinru Song , Xiaoyu Bu , Xiaohui Zhao , Rongxiang Zhang , Shang Wang , Fulong Dong

Second harmonic generation (SHG) is forbidden in centrosymmetric molecular materials. However, a signal is frequently observed from interfaces where the symmetry is broken. Whereas the effect can be phenomenologically accommodated, an ab…

We demonstrate second harmonic generation (SHG) in an $x$-cut congruent lithium niobate (LN) whispering gallery mode resonator. We first show theoretically that independent control of the coupling of the pump and signal modes is optimal for…

The nonlinear forcing terms for the wave equation in general curvilinear coordinates are derived based on a hyperelastic material. The expressions for the nonlinear part of the first Piola-Kirchhoff stress are specialized for axisymmetric…

Classical Physics · Physics 2012-09-20 Yang Liu , Ehsan Khajeh , Cliff J. Lissenden , Joseph L. Rose

We discuss a novel method for generating octave-spanning supercontinua and few-cycle pulses in the important mid-IR wavelength range. The technique relies on strongly phase-mismatched cascaded second-harmonic generation (SHG) in mid-IR…

Optics · Physics 2013-12-04 M. Bache , H. Guo , B. Zhou

Generation of second-harmonic waves is one of the universal nonlinear phenomena that have found numerous technical applications in many modern technologies, in particular, in photonics. This phenomenon also has great potential in the field…

Mesoscale and Nanoscale Physics · Physics 2024-03-01 K. O. Nikolaev , S. R. Lake , G. Schmidt , S. O. Demokritov , V. E. Demidov

We propose novel multi-phase-matched process that starts with generation of a pair of symmetric second-harmonic waves. Each of them interacts again with the fundamental wave to produce two constructively interfering third harmonic waves…

Optics · Physics 2009-11-10 Todor Karaulanov , Solomon M. Saltiel

The efficient generation of terahertz (THz) waves in two-dimensional (2D) MXene layers driven by near-infrared femtosecond laser pulses is demonstrated through predictive simulations. Employing a novel hydrodynamic model that…

Optics · Physics 2025-12-23 A. A. Molavi Choobini , A. Chimeh

A comprehensive analysis of second harmonic generation (SHG) in a diatomic zincblende crystal based on the Simplified Bond Hyperpolarizability Model (SBHM), Group Theory (GT) is presented. The third rank tensor between the two approaches…

Plasmonic enhancement of nonlinear optical processes confront severe limitations arising from the strong dispersion of metal susceptibilities and small interaction volumes that hamper desirable phase-matching-like conditions. Maximizing…

The gravitational wave (GW) background produced at the cosmological chiral phase transition in a conformal extension of the standard model is studied. To obtain the bounce solution of coupled field equations we implement an iterative…

High Energy Physics - Phenomenology · Physics 2020-04-15 Mayumi Aoki , Jisuke Kubo

A model of localized electron wave packets (EWPs), floating and breathing Gaussians with non-orthogonal valence-bond spin-coupling, is applied to compute the high-harmonic generation (HHG) spectrum from a LiH molecule induced by an intense…

Chemical Physics · Physics 2018-03-07 Koji Ando

We identify analytically a multiple-peak structure in the energy-density spectrum of induced gravitational waves (GWs) generated at second-order from a primordial scalar perturbations also with multiple($n$) peaks at small scales $k_{*i}$.…

Cosmology and Nongalactic Astrophysics · Physics 2019-05-13 Rong-Gen Cai , Shi Pi , Shao-Jiang Wang , Xing-Yu Yang
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