Plasma Dynamics Characterization for Improvement of Resonantly Enhanced Harmonics Generation in Indium and Tin Laser-Produced Plasmas

R.A.G. is grateful to H. Kuroda for providing the access to the laser facility. As a Center of Excellence, the Institute of Solid State Physics at the University of Latvia received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement no. 739508, project CAMART².In this study, we characterize the properties of indium and tin laser-induced plasmas responsible for efficient high-order harmonics generation of the ultrashort pulses propagating through these media. The optimally formed plasma was determined using the analysis of the time-resolved variations in the spectral and morphological features of spreading indium and tin plasma components under different regimes of laser ablation. We report the measurements of plasma velocities under different regimes of ablation and correlate them with the optimal delay between the heating and probe laser pulses for the generation of harmonics with the highest yield. Electron temperatures and densities are determined using the integrated and time-resolved spectral measurements of plasmas. The resonance-enhanced harmonics are compared with other harmonics from the point of view of the modulation of plasma characteristics. The harmonics of 800 and 1200–2200 nm lasers and their second-harmonic fields were analyzed at optimal conditions of Sn and In plasma formation. The novelty of this work is the implementation of the diagnostics of the dynamics of plasma characteristics for the determination of the optimal plasma formation for harmonics generation. Such an approach allows for the demonstration of the maximal harmonic yield from the studied plasma and the definition of the various resonance-induced harmonic generation conditions. © 2022 by the authors.European Regional Development Fund (1.1.1.5/19/A/003); Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2

Variation of Nonlinear Refraction and Three-Photon Absorption of Indium–Tin Oxide Quantum Dot Thin Films and Solutions in Near Infrared Range

Authors acknowledge the support of J. Grube and A. Sarakovskis in providing the laser facility for these studies. Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.We characterize the nonlinear optical properties of indium–tin oxide (ITO) quantum dots (QDs) in the IR range using the Z-scan method. We present results of three-photon absorption (3PA), third harmonic generation (3HG), and Kerr-effect-induced nonlinear refraction in ITO QDs. Z-scan measurements were carried out for the QDs solution, while 3HG was demonstrated using QD thin films. The Kerr-induced nonlinear refractive index was analyzed along the 800–950 nm range showing an increase in this parameter from −6.7 × 10−18 to −1.5 × 10−17 m2 W−1. At longer wavelengths (1000–1100 nm), the higher-order effects started to contribute to a nonlinear refractive index. The 3PA coefficient at 950 nm was measured to be 1.42 × 10−25 m3/W2. We discuss the peculiarities in the wavelength-dependent variation of the coefficient of nonlinear absorption responsible for 3PA in the range of 800–1150 nm. Third harmonic generation was analyzed in the 1200–1550 nm spectral range. The absolute value of 3HG conversion efficiency in the 150 nm thick film at the wavelength of laser radiation (1350 nm) was estimated to be ~10–5. --//-- This is an open access article Bundulis, A.; Berzina, A.; Kim, V.V.; Polyakov, B.; Novikovs, A.; Ganeev, R.A. Variation of Nonlinear Refraction and Three-Photon Absorption of Indium–Tin Oxide Quantum Dot Thin Films and Solutions in Near Infrared Range. Nanomaterials 2023, 13, 2320. https://doi.org/10.3390/nano13162320 published under the CC BY 4.0 licence.Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

High-order harmonics generation in Cd and Pd laser-induced plasmas

R.A.G. is grateful to H. Kuroda for providing access to the laser facility. Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.We demonstrate the generation of high-order harmonics of laser pulses in palladium and cadmium plasmas. We adjusted the wavelength of driving pulses to investigate the resonance enhancement in different ranges of extreme ultraviolet region. The summation of incommensurate waves during the two-color pump of Pd and Cd plasmas allowed the generation of a broader range of harmonics. The theoretical aspects of the two-color pump of the laser-induced plasma are discussed. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement --//-- This is an open access article Rashid A. Ganeev, Vyacheslav V. Kim, Jelena Butikova, Aigars Atvars, Jurgis Grube, Anatolijs Sarakovskis, and Arnolds Ubelis, "High-order harmonics generation in Cd and Pd laser-induced plasmas," Opt. Express 31, 26626-26642 (2023), https://doi.org/10.1364/OE.493754 published under the CC BY 4.0 licence.European Regional Development Fund (1.1.1.5/19/A/003); World Bank Project (REP-04032022-206).Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Nonlinear absorption and refraction of picosecond and femtosecond pulses in HgTe quantum dot films

We report measurements of the saturated intensities, saturable absorption, and nonlinear refraction in 70-nm thick films containing 4 nm HgTe quantum dots. We demonstrate strong nonlinear refraction and saturable absorption in the thin films using tunable picosecond and femtosecond pulses. Studies were carried out using tunable laser pulses in the range of 400–1100 nm. A significant variation of the nonlinear refraction along this spectral range was demonstrated. The maximal values of the nonlinear absorption coefficients and nonlinear refractive indices determined within the studied wavelength range were −2.4 × 10−5 cm2 W−1 (in the case of 28 ps, 700 nm probe pulses) and −3 × 10−9 cm2 W−1 (in the case of 28 ps, 400 nm probe pulses), respectively. Our studies show that HgTe quantum dots can be used in different fields e.g., as efficient emitters of high-order harmonics of ultrashort laser pulses or as laser mode-lockers. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Published under the CC BY 4.0 license.European Regional Development Fund (1.1.1.5/19/A/003), Latvian Council of Sciences (lzp-2020/2-0238). Institute of Solid State Physics, University of Latvia as the Center of Excellence acknowledges funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

High-order harmonic generation from laser induced plasma comprising CdSe/V2O5 Core/Shell quantum dots embedded on MoS2 nanosheets

Research of the nonlinear optical characteristics of transition metal dichalcogenides in the presence of photoactive particles, plasmonic nanocavities, waveguides, and metamaterials is still in its early stages. This investigation delves into the high-order harmonic generation (HHG) from laser induced plasma of MoS2 nanosheets in the presence of semiconductor photoactive medium such as CdSe and CdSe/V2O5 core/shell quantum dots. Our comprehensive findings shed light on the counteractive coupling impact of both bare and passivated quantum dots on MoS2 nanosheets, as evidenced by the emission of higher-order harmonics. Significantly, the intensity of harmonics and their cut-off were notably enhanced in the MoS2-CdSe and MoS2-V-CdSe configurations compared to pristine MoS2 nanosheets. These advancements hold promise for applications requiring the emission of coherent short-wavelength radiation.Comment: 8 pages, 4 figure

Charge transfer mechanism on MoS2_2 nanosheets in the presence of a semiconductor photoactive media

The studies of the nonlinear optical (NLO) properties of the transition metal dichalcogenides (TMDs) coupled with photoactive particles, plasmonic nanocavities, waveguides, and metamaterials remain in their infancy. This study investigates the third-order NLO properties of MoS$_2$ nanosheets in the presence of a semiconductor photoactive medium. Our extensive studies and the obtained results reveal the counteractive coupling effect of bare and passivated quantum dots on the MoS$_2$ nanosheet, as made evident by the analysis of the NLO processes. The enhanced NLO properties of MoS$_2$ nanosheets functionalized with CdSe and CdSe-V2O5 quantum dots are helpful for applications as saturable absorbers in laser applications and the emission of coherent short-wavelength radiation. The multiphoton-excitation resonance energy transfer mechanism exploiting remote dipole dipole coupling, and ultrafast charge transfer pathways emerges as another plausible way to alter the NLO properties in TMDs.Comment: 16 pages, 4 figure

Laser-surface interactions

This book is about the interaction of laser radiation with various surfaces at variable parameters of radiation. As a basic principle of classification we chose the energetic or intensity level of interaction of laser radiation with the surfaces. These two characteristics of laser radiation are the most important parameters defining entire spectrum of the processes occurring on the surfaces during interaction with electromagnetic waves. This is a first book containing a whole spectrum of the laser-surface interactions distinguished by the ranges of used laser intensity. It combines the surface response starting from extremely weak laser intensities (~1 W cm-2) up to the relativistic intensities (~1020 W cm-2 and higher). The book provides the basic information about lasers and acquaints the reader with both common applications of laser-surface interactions (laser-related printers, scanners, barcode readers, discs, material processing, military, holography, medicine, etc) and unusual uses of the processes on the surfaces under the action of lasers (art conservation, rangefinders and velocimeters, space and earth explorations, surface engineering and ablation, and others). The scientific applications of laser-surfaces interactions (surface optical nonlinearities, surface enhanced Raman spectroscopy, surface nanostructuring, nanoripples and clusters formation, X-ray lasers and harmonic generation from the surfaces) are discussed from the point of view of the close relations between the properties of surface and matter, which is a cornerstone of most of studies of materials. The novelty of the approach developed in Laser - Surface Interactions is related with the interconnection of scientific studies with numerous applications of the laser-surface interactions separated in different chapters by the ranges of laser intensities. We present most recent achievements in this field. The book provides valuable information for different ranges of reader's preparedness to the laser-related topics (from unprepared readers, to students, engineers and researchers, professionals and academics)