Effects of Laser Plasma Formation on Quasi-Phase Matching of High-Order Harmonics from Nanoparticles and Atoms

The application of nanoparticles (NPs) and quasi-phase matching (QPM) each play an important role in the enhancement of high-order harmonics (HHG) of ultrashort laser pulses. We analyze various regimes of nanoparticle plasma formation for the creation conditions for maximal QPM-induced enhancement of the groups of harmonics in the extreme ultraviolet (XUV). Laser plasmas were formed on the surfaces of NPs- and microparticle (MPs)-contained targets using ablation by nanosecond, picosecond, and femtosecond pulses. Different conditions of laser plasma formation (extended and perforated plasma) and variable concentrations of free electrons in these three cases of laser ablation led to modifications of QPM conditions. We demonstrate novel approaches in the optimization of QPM at the conditions of laser ablation of NPs and MPs by pulses of different durations. The formation of QPM conditions using femtosecond and picosecond heating pulses during HHG in such plasmas allowed the growth of conversion efficiency of the groups of harmonics, with the enhancement factors exceeding 25× in different ranges of XUV, contrary to less efficient QPM in the case of nanosecond pulse-induced ablation.

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Application of Quasi-Phase Matching Concept for Enhancement of High-Order Harmonics of Ultrashort Laser Pulses in Plasmas

Applied Sciences ◽

10.3390/app9081701 ◽

2019 ◽

Vol 9 (8) ◽

pp. 1701 ◽

Cited By ~ 3

Author(s):

R. A. Ganeev ◽

S. Y. Stremoukhov ◽

A. V. Andreev ◽

A. S. Alnaser

Keyword(s):

Extreme Ultraviolet ◽

Laser Pulses ◽

Plasma Jets ◽

High Order ◽

Ultrashort Laser Pulses ◽

Phase Matching ◽

Quasi Phase Matching ◽

Fundamental Radiation ◽

Formation Conditions ◽

The One

Novel methods of coherent short-wavelength sources generation require thorough analysis for their further amendments and practical implementations. In this work, we report on the quasi-phase matching (QPM) of high-order harmonics generation during the propagation of single- and two-color femtosecond pulses through multi-jet plasmas, which allows the enhancement of groups of harmonics in different ranges of extreme ultraviolet. The role of the number of coherent zones; sizes of plasma jets and the distance between them; plasma formation conditions, and the characteristics of the fundamental radiation on the harmonic efficiency at quasi-phase matching (QPM) conditions are analyzed. We demonstrate the ~40× enhancement factor of the maximally-enhanced harmonic with respect to the one generated at ordinary conditions in the imperforated plasma.

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Low- and High-Order Nonlinear Optical Characterization of Metal Sulfide Quantum Dots -=SUP=-*-=/SUP=-

Журнал технической физики ◽

10.21883/os.2019.08.48044.96-19 ◽

2019 ◽

Vol 127 (8) ◽

pp. 291

Author(s):

R.A. Ganeev

Keyword(s):

Quantum Dots ◽

Nonlinear Optical ◽

Extreme Ultraviolet ◽

Nonlinear Refraction ◽

Metal Sulfide ◽

Laser Pulses ◽

High Order ◽

Ultrashort Laser Pulses ◽

Practical Applications ◽

Ultraviolet Range

Any new synthesized semiconductor nanoparticles or quantum dots (QDs) require to be examined under different conditions using laser pulses of variable energies, wavelengths and durations to understand the nonlinear optical mechanisms and distinguish their attractive properties for practical applications. Among various QDs the metal sulfides took special attention due to their advanced nonlinear optical properties. Additionally, laser ablation can readily produce plasmas containing QDs that could be used for different applications. One of them is that they can be used as emitters for harmonic generation from ultrashort laser pulses. Here we review recent studies of different low- and high-order optical nonlinearities of metal sulfide QDs, such as optical limiting, two-photon, saturable and reverse saturable types of nonlinear absorption, nonlinear refraction, and generation of high-order harmonics in extreme ultraviolet range.

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