Article
Materials Science, Multidisciplinary
S. Grisard, H. Rose, A. V. Trifonov, R. Reichhardt, D. E. Reiter, M. Reichelt, C. Schneider, M. Kamp, S. Hofling, M. Bayer, T. Meier, I. A. Akimov
Summary: We study Rabi rotations in intensity-dependent photon echoes from a group of self-assembled InGaAs quantum dots. By using flattop intensity profiles of picosecond laser pulses, we are able to achieve a uniform distribution of intensities within the excited group and overcome the damping effect caused by the spatial inhomogeneity of Rabi frequencies from a Gaussian laser profile. Through photon echo polarimetry, we differentiate the coherent optical responses from exciton and trion groups. We find that the charging of the quantum dots under resonant excitation with intensive optical pulses leads to a significant reduction in the number of neutral quantum dots, while the trion group exhibits robust Rabi rotations with increased refocussing pulse areas. The remaining attenuation of Rabi rotations is analyzed through theoretical modeling, considering excitation-induced dephasing, dipole moment inhomogeneity, and coupling to acoustic phonons, revealing the dominant mechanism of optical coherence loss during the action of the involved optical pulses.
Article
Optics
Pan Wei, Zhong Guan, Ling-Ling Du, Zhi-Hong Jiao, Lei Zhang, Guo-Li Wang, Shi-Lin Hu, Song-Feng Zhao
Summary: The paper theoretically studied the fine subpeak structures in the below-threshold harmonic spectra of stretched H-2 and N-2 molecules, identifying their origin in Rabi-flopping between the ground state and first excited state. It was confirmed that such subpeak structures are common in molecules at large internuclear distances when two molecular states are strongly coupled. Additionally, the spacing between adjacent subpeaks in these spectra can be determined approximately by analyzing the induced dipole moment in the time domain.
Article
Materials Science, Multidisciplinary
R. Zhou, T. Guo, L. Huang, K. Ullah
Summary: In the field of nonlinear optics, graphene has demonstrated remarkable nonlinear properties, particularly in harmonic generation (HG). This review presents the latest achievements in engineering graphene's HG and discusses various strategies to tune and enhance it. Graphene exhibits the largest nonlinear optical susceptibilities compared to other materials, making it a promising candidate for the development of broadband, ultrafast optical devices.
MATERIALS TODAY PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
H. K. Avetissian, S. Sukiasyan, H. H. Matevosyan, G. F. Mkrtchian
Summary: The objective of this article is to investigate the profound nonlinear optical response exhibited by inversion symmetric fullerene molecules under the influence of different types of disorders described by the Anderson model. The disorder-induced effects are imprinted onto molecules' high-harmonic spectrum, and even-order harmonic signals are observed for relatively small disorders. Both diagonal and off-diagonal disorders lift the degeneracy of states, leading to the enhancement of the high-harmonic emission. The second harmonic intensity exhibits a quadratic scaling with the disorder strength, enabling the usage of the harmonic spectrum as a tool in measuring the type and the strength of a disorder.
RESULTS IN PHYSICS
(2023)
Article
Optics
L. Kelley, Z. Germain, E. C. Jones, D. Milliken, Barry C. Walker
Summary: This study addresses the challenge of finding the optimal laser intensity and wavelength to achieve high-energy, strong field rescattering, and reports maximum yields of hole creation in both K-shell and L-I shell. The results show a simple scaling of peak rescattering with atomic number and laser wavelength, suggesting a possibility to describe ideal laser parameters for general high-energy laser rescattering processes.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Irati Alonso Calafell, Lee A. Rozema, Alessandro Trenti, Justus Bohn, Eduardo J. C. Dias, Philipp K. Jenke, Kishan S. Menghrajani, David Alcaraz Iranzo, F. Javier Garcia de Abajo, Frank H. L. Koppens, Euan Hendry, Philip Walther
Summary: This study investigates high-harmonic generation in graphene heterostructures and discovers that metallic nanoribbons can amplify near-field effects in the graphene layer, allowing the observation of third- and fifth-harmonic generation in the mid-infrared pump power. The study also finds that ribbon width, spacer thickness, pump power, and polarization have an impact on the nonlinear signals, and demonstrates enhancement factors for third- and fifth-harmonic generation relative to bare graphene.
ADVANCED OPTICAL MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Wentao Wu, Shuo Tang
Summary: This study presents theoretical analyses of harmonic generation with a focused Gaussian beam. Analytical solutions are obtained for the integral of the phase-matching factor which can be applied to various focusing and sample conditions. The study shows that reasonable SHG and THG efficiency can be excited near interfaces or for thin samples with normal dispersion. An optimization process of the confocal parameter is proposed based on the properties of the sample. Multimodal label-free imaging combining SHG, THG, and two-photon excitation fluorescence is demonstrated on biological samples for acquiring complementary information about tissues.
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
(2023)
Article
Optics
Haiying Yuan, Yujun Yang, Fuming Guo, Jun Wang, Jigen Chen, Wei Feng, Zhiwen Cui
Summary: The interaction between ultrashort intense laser pulses and atoms can reveal the ultrafast dynamics of electrons through photoelectron emission spectra. By using the numerical solution of the time-dependent Schrodinger equation in momentum space, the photoelectron emission spectra of atoms irradiated by 400 nm intense lasers with different durations have been studied. The observed photoelectron peaks originate from the ionization of the excited state and their oscillations are due to the superposition with the sideband energy positions. The energy positions of the maximum intensity of the photoelectron emission spectra move towards higher energy end as the duration of the driving laser pulse extends.
Article
Optics
Alexander W. A. Murphy, Zichen Liu, Andrey V. Gorbach, Adelina Ilie, Ventsislav K. Valev
Summary: The study presents the first hyperspectral multiphoton analysis of densely-packed stacks of twisted and/or fused WS2 nanosheets, known as nanomesh, which exhibits scalable, efficient, and broadband optical properties due to double resonances induced by internal defects. This makes the nanomesh a prime candidate for integration into quantum optical technologies.
LASER & PHOTONICS REVIEWS
(2021)
Article
Optics
Yuntian Zhang, Liang Li, Jiapeng Li, Tengfei Huang, Pengfei Lan, Peixiang Lu
Summary: By solving the semiconductor Bloch equations, we investigate the orientation dependence of high-order harmonic generation in graphene, discovering different patterns for different harmonics. As the laser intensity increases, these patterns become similar, except for a double-peak structure in lower-order harmonics.
Article
Multidisciplinary Sciences
Kunze Lu, Manlin Luo, Weibo Gao, Qi Jie Wang, Hao Sun, Donguk Nam
Summary: Despite the centrosymmetric nature of graphene, strain engineering can be used to manipulate its lattice arrangement and induce sublattice polarization, activating second harmonic generation (SHG). The SHG signal in strained graphene is boosted 50-fold at low temperatures due to resonant transitions between strain-induced pseudo-Landau levels. The second-order susceptibility of strained graphene exceeds that of hexagonal boron nitride with intrinsic broken inversion symmetry, opening up possibilities for high-efficiency nonlinear devices.
NATURE COMMUNICATIONS
(2023)
Article
Optics
Shan Zhu, Jiaqi Quan, Yangyang Fu, Huanyang Chen, Lei Gao, Yadong Xu
Summary: In this work, a modified diffraction law is proposed to describe nonlinear diffraction phenomena by involving the reciprocal lattice effect of nonlinear metasurfaces. The law is numerically demonstrated and confirmed by designed graphene-based nonlinear metasurfaces in the terahertz regime. Additionally, a nonlinear retroreflector is designed based on the diffraction law, allowing tunable control over a nonlinear wavefront in a single nonlinear metasurface.
Article
Multidisciplinary Sciences
Markus Seeger, Antonios Stylogiannis, Ludwig Prade, Sarah Glasl, Vasilis Ntziachristos
Summary: By using overdriving continuous-wave laser diodes and frequency-wavelength multiplexing based on illumination pulse-trains, we demonstrate concurrent multi-wavelength optoacoustic microscopy with high signal-to-noise ratios and high resolution, allowing visualization of vascular oxygenation dynamics and circulating tumor cells.
SCIENTIFIC REPORTS
(2023)
Article
Optics
Chenglin Wang, Andrey Novitsky, Wenxuan Ge, Dongliang Gao, Lei Gao
Summary: In this paper, high second-harmonic generation (SHG) conversion efficiency is achieved by combining the strong second-order nonlinear effects of graphene and the field-enhancing effects of anisotropic materials. The nonlinear conversion efficiency of radial anisotropic nanoparticles is found to be several orders of magnitude higher than that of isotropic counterpart, due to the additional enhancement of field intensity near the boundary provided by radial anisotropic and the presence of graphene at the particle boundary where the fundamental frequency field is significantly enhanced. Moreover, the highly tunable characteristic of graphene offers additional flexibility for manipulating the SHG spectrum in practical applications.
Article
Chemistry, Physical
Francois Aguillon, Andrei G. Borisov
Summary: In this work, the impact of atomic scale lattice imperfections on the nonlinear response of graphene nanoflakes enhanced by resonance between electromagnetic fields and localized plasmon is investigated theoretically. Using the many-body time-dependent density matrix approach, it is found that a single defect in nanoflakes with thousands of carbon atoms can significantly affect the nonlinear hyperpolarizability and override symmetry constraints. This effect cannot be captured by the relaxation time approximation in quantum or classical frameworks. The results of this study have important implications for the design of nonlinear graphene devices.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Nanoscience & Nanotechnology
Hamlet K. Avetissian, Ara K. Avetissian, Armenuhi G. Ghazaryan, Garnik F. Mkrtchian, Khachik Sedrakian
JOURNAL OF NANOPHOTONICS
(2020)
Article
Nanoscience & Nanotechnology
Hamlet K. Avetissian, Babken R. Avchyan, Garnik F. Mkrtchian, Karine A. Sargsyan
JOURNAL OF NANOPHOTONICS
(2020)
Article
Optics
H. K. Avetissian, B. R. Avchyan, H. H. Matevosyan, G. F. Mkrtchian
Summary: This paper explores a potential method to achieve laser emission from THz to extreme UV regions using graphene plasmons stimulated by free electrons. The analytical-quantitative description is based on a set of self-consistent Maxwell-Vlasov equations. Both downconversion and upconversion processes are studied, demonstrating the feasibility of coherent conversion between different radiation wavelengths.
Article
Materials Science, Multidisciplinary
H. K. Avetissian, V. A. Sedrakyan, Kh. V. Sedrakian, G. F. Mkrtchian
Summary: We study the coherent dynamics of charged carriers in graphene under intense few-cycle linearly polarized laser pulses. By numerically solving the generalized semiconductor Bloch equations considering many-body Coulomb interaction in the Hartree-Fock approximation, we find a strong dependence of valley polarization on the carrier-envelope phase (CEP) following a simple sinusoidal law. Moreover, we investigate harmonic generation in graphene exposed to a multicycle laser field and show that the intensity of the second harmonic provides a reliable measure of CEP for pulse durations up to two optical cycles (40 fs at 6.2 μm wavelength).
Article
Optics
H. K. Avetissian, V. N. Avetisyan, B. R. Avchyan, G. F. Mkrtchian
Summary: This paper investigates the nonlinear interaction between a Weyl semimetal and a strong driving electromagnetic wave field, analyzing the high-order harmonic generation spectra in the Weyl semimetal with broken time-reversal symmetry. The results show that the spectra in the Weyl semimetal are completely different compared to the two-dimensional graphene case.
Article
Materials Science, Multidisciplinary
Hamlet K. Avetissian, Garnik F. Mkrtchian, Andreas Knorr
Summary: This study investigates high-order frequency mixing in graphene using a two-color radiation field. The results show that the generation of harmonics from interband transitions is more efficient in the case of an orthogonally polarized two-color field. The generated high harmonics are over two orders of magnitude stronger than those obtained in the parallel polarization case. This is in contrast to atomic and semiconductor systems, where the parallel polarization case is more preferable.
Article
Materials Science, Multidisciplinary
H. K. Avetissian, A. G. Ghazaryan, G. F. Mkrtchian
Summary: Using dynamical Hartree-Fock mean-field theory, the high harmonic generation (HHG) in fullerene molecules C-60 and C-70 under strong pump wave driving was studied. It was found that the output harmonic radiation exhibits multiple plateaus, defined by molecular excitonic lines, and the cutoff energies scale linearly with the field strength amplitude within each plateau. Increase in pump wave photon energy leads to higher cutoff harmonic energy, while increase in electron-electron interaction energy suppresses overall HHG rate. C-70 molecule shows richer HHG spectra and stronger high harmonic intensity compared to C-60.
Article
Physics, Multidisciplinary
Malte Selig, Florian Katsch, Samuel Brem, Garnik F. Mkrtchian, Ermin Malic, Andreas Knorr
PHYSICAL REVIEW RESEARCH
(2020)
Article
Physics, Multidisciplinary
H. K. Avetissian, G. F. Mkrtchian, K. Z. Hatsagortsyan
PHYSICAL REVIEW RESEARCH
(2020)
Article
Materials Science, Multidisciplinary
H. K. Avetissian, G. F. Mkrtchian
Article
Materials Science, Multidisciplinary
H. K. Avetissian, G. F. Mkrtchian, K. G. Batrakov, S. A. Maksimenko
Article
Materials Science, Multidisciplinary
Garnik F. Mkrtchian, Andreas Knorr, Malte Selig
Article
Materials Science, Multidisciplinary
H. K. Avetissian, A. K. Avetissian, B. R. Avchyan, G. F. Mkrtchian
Article
Materials Science, Multidisciplinary
H. K. Avetissian, G. F. Mkrtchian
Article
Materials Science, Multidisciplinary
H. K. Avetissian, G. F. Mkrtchian
