scholarly journals Ultrafast laser heating of non-plasmonic nanocylinders

2021 ◽  
Vol 2015 (1) ◽  
pp. 012104
Author(s):  
Olesia Pashina ◽  
Daniil Ryabov ◽  
George Zograf ◽  
Sergey Makarov ◽  
Mihail Petrov

Abstract We develop a model describing non-equilibrium processes under the excitation of resonant semiconductor nanostructures with ultrashort laser pulses with a duration of about 100 fs. We focus on the heating effects related to pulsed excitation with account on free carriers generation, thermalization, and relaxation. The heat exchange between the electron and phonon system is treated within the two-temperature model. We applied the developed model to describing pulsed heating of silicon nanocylinder on top of a dielectric substrate. We come up with estimations of the thermal damage threshold of the considered structures which provides the limits for the experimental conditions and ensures thermal stability of the samples.

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 754
Author(s):  
Igor Kinyaevskiy ◽  
Pavel Danilov ◽  
Nikita Smirnov ◽  
Sergey Kudryashov ◽  
Andrey Koribut ◽  
...  

Ablation of BaWO4 Raman crystals with different impurity concentrations by ultrashort laser pulses was experimentally studied. Laser pulses with duration varying from 0.3 ps to 1.6 ps at wavelengths of 515 nm and 1030 nm were applied. A single-pulse optical damage threshold of the crystal surface changed from 1.3 J/cm2 to 4.2 J/cm2 depending on the laser pulse parameters and BaWO4 crystal purity. The optical damage threshold under multi-pulse irradiation was an order of magnitude less.


Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1186
Author(s):  
Ayesha Sharif ◽  
Nazar Farid ◽  
Rajani K. Vijayaraghavan ◽  
Patrick J. McNally ◽  
Gerard M. O’Connor

We propose a novel low temperature annealing method for selective crystallization of gold thin films. Our method is based on a non-melt process using highly overlapped ultrashort laser pulses at a fluence below the damage threshold. Three different wavelengths of a femtosecond laser with the fundamental (1030 nm), second (515 nm) and third (343 nm) harmonic are used to crystallize 18-nm and 39-nm thick room temperature deposited gold thin films on a quartz substrate. Comparison of laser wavelengths confirms that improvements in electrical conductivity up to 40% are achievable for 18-nm gold film when treated with the 515-nm laser, and the 343-nm laser was found to be more effective in crystallizing 39-nm gold films with 29% improvement in the crystallinity. A two-temperature model provides an insight into ultrashort laser interactions with gold thin films and predicts that applied fluence was insufficient to cause melting of gold films. The simulation results suggest that non-equilibrium energy transfer between electrons and lattice leads to a solid-state and melt-free crystallization process. The proposed low fluence femtosecond laser processing method offers a possible solution for a melt-free thin film crystallization for wide industrial applications.


2021 ◽  
Vol 2094 (2) ◽  
pp. 022023
Author(s):  
G V Mikheeva ◽  
A V Pashin

Abstract A numerical study of heat transfer between an electron gas and a crystal lattice in a metal nanofilm under irradiation with an ultrashort laser pulse was carried out on the basis of a parabolic two-temperature model of thermal conductivity presented in a dimensionless form. For the numerical solution, the finite difference method was used using the explicit-implicit Crank-Nicholson scheme. As a result of the numerical study, it was found that with an increase in the thickness of the plate, the equilibrium temperature decreases, and the time for the onset of thermal equilibrium between the electrons and the crystal lattice increases.


Author(s):  
Isamu Miyamoto ◽  
Kristian Cvecek ◽  
Yasuhiro Okamoto ◽  
Michael Schmidt ◽  
Henry Helvajian

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