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@@ -132,7 +132,7 @@
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& \noindent\large{Anton Rudenko,$^{\ast}$\textit{$^{a}$} Konstantin Ladutenko,\textit{$^{b}$} Sergey Makarov\textit{$^{b}$} and Tatiana E. Itina\textit{$^{a}$$^{b}$}
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\textit{$^{a}$~Laboratoire Hubert Curien, UMR CNRS 5516, University of Lyon/UJM, 42000, Saint-Etienne, France }
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- \textit{$^{b}$~ITMO University, Kronverksiy pr. 49, St. Petersburg, Russia}
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+ \textit{$^{b}$~ITMO University, Kronverksiy pr. 49, Saint-Petersburg, Russia}
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} \\%Author names go here instead of "Full name", etc.
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@@ -147,7 +147,7 @@
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regime of simultaneous excitation of electric and magnetic Mie
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resonances, resulting in an effective transient reconfiguration of
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nanoparticle scattering properties. However, only homogeneous plasma
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- generation was previously considered in the photo-excited
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+ generation was previously considered in a photo-excited
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nanoparticle, remaining unexplored any effects related to the
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plasma-induced optical inhomogeneities. Here we examine these
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effects by using 3D numerical modeling of coupled electrodynamic and
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@@ -215,8 +215,8 @@ modulation~\cite{iyer2015reconfigurable, makarov2015tuning,
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all-dielectric nanoantennas and metasurfaces possess much smaller
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parasitic Joule losses at high intensities as compared with their
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plasmonic counterparts, whereas their nonlinear properties are
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-comparable. More importantly, the unique properties of the nonlinear
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-all-dielectric nanodevices are due to the existance of both electric and
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+comparable. More importantly, the unique properties of nonlinear
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+all-dielectric nanodevices are due to the existence of both electric and
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magnetic optical resonances in visible and near IR
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ranges~\cite{kuznetsov2016optically}. For instance, even slight
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variation of dielectric permittivity around optical resonances leads
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@@ -253,7 +253,7 @@ symmetry of nanoparticles can be reduced.
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In this Letter, we show theoretically that ultra-fast photo-excitation
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in a spherical silicon NP leads to a strongly inhomogeneous EHP
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-distribution, as schematically shown in Fig.~\ref{fgr:concept}. To
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+distribution, as is shown schematically in Fig.~\ref{fgr:concept}. To
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reveal and analyze this effect, we perform a full-wave numerical
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simulation. We consider an intense femtosecond (\textit{fs}) laser
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pulse to interact with a silicon NP supporting Mie resonances and
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@@ -295,9 +295,9 @@ advantage is based on a broad range of optical nonlinearities, strong
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two-photon absorption, as well as a possibility of the photo-induced
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EHP excitation~\cite{leuthold2010nonlinear}. Furthermore, silicon
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nanoantennas demonstrate a sufficiently high damage threshold due to
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-the large melting temperature ($\approx 1690$~K), whereas its nonlinear
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-optical properties have been extensively studied during last
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-decays~\cite{Van1987, Sokolowski2000, leuthold2010nonlinear}. High
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+the high melting temperature ($\approx 1690$~K), whereas its nonlinear
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+optical properties were extensively studied during the last
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+decades~\cite{Van1987, Sokolowski2000, leuthold2010nonlinear}. High
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silicon melting point typically preserves structures formed from this
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material up to the EHP densities on the order of the critical value
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$N_{cr} \approx 5\cdot{10}^{21}$~cm$^{-3}$ \cite{Korfiatis2007}. At
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@@ -372,8 +372,8 @@ Gaussian slightly focused beam as follows
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\end{aligned}
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\end{align}
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where $\theta \approx 130$~\textit{fs} is the temporal pulse width at
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-the half maximum (FWHM), $t_0$ is a time delay, $w_0 = 3{\mu}m$ is the
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-waist beam, $w(z) = {w_0}\sqrt{1+(\frac{z}{z_R})^2}$ is the Gaussian's
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+the half maximum (FWHM), $t_0$ is the time delay, $w_0 = 3{\mu}m$ is the
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+beam waist, $w(z) = {w_0}\sqrt{1+(\frac{z}{z_R})^2}$ is the Gaussian's
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beam spot size, $\omega = 2{\pi}c/{\lambda}$ is the angular frequency,
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$\lambda = 800$~nm is the laser wavelength in air, $c$ is the speed of
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light, ${z_R} = \frac{\pi{{w_0}^2}n_0}{\lambda}$ is the Rayleigh
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@@ -403,7 +403,7 @@ $I=\frac{n}{2}\sqrt{\frac{\epsilon_0}{\mu_0}}\left|\vec{E}\right|^2$
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is the intensity, $\sigma_1 = 1.021\cdot{10}^3$~cm$^{-1}$ and
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$\sigma_2 = 0.1\cdot{10}^{-7}$~cm/W are the one-photon and two-photon
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interband cross-sections \cite{Choi2002, Bristow2007, Derrien2013},
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-$N_a = 5\cdot{10}^{22}$~cm$^{-3}$ is the saturation particle density
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+$N_a = 5\cdot{10}^{22}$~cm$^{-3}$ is the particle saturation density
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\cite{Derrien2013}, $C = 3.8\cdot{10}^{-31}$~cm$^6$/s is the Auger
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recombination rate \cite{Van1987}, $\tau_{rec} = 6\cdot{10}^{-12}$~s
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is the minimum Auger recombination time \cite{Yoffa1980}, and
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@@ -526,13 +526,13 @@ GitHub~\cite{Scattnlay-web} under open source license.
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the intensity is enhanced in the back side of the NP as demonstrated
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in Fig.~\ref{mie-fdtd}(d). In fact, rather similar EHP distributions
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can be obtained by applying Maxwell's equations coupled with the rate
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- equation for relatively weak excitation with EHP concentration of
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+ equation for a relatively weak excitation with EHP concentration of
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$N_e \approx 10^{20}$~cm$^{-3}$, see Fig.~\ref{mie-fdtd}(e,f). The
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optical properties do not change considerably due to the excitation
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according to (\ref{Index}). Therefore, the excitation processes
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follow the intensity distribution. However, such coincidence was
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achieved under quasi-stationary conditions, after the electric field
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- made enough oscillations inside the Si NP. Further on we present
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+ made enough oscillations inside the Si NP. Further on, we present
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transient analysis, which reveals much more details.
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To achieve a quantitative description for evolution of the EHP
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@@ -551,7 +551,7 @@ GitHub~\cite{Scattnlay-web} under open source license.
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be justified. In what follows, we discuss the results of the
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numerical modeling of the temporal evolution of EHP densities and the
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asymmetry factors $G_{N_e}$ for different sizes of Si NP, as shown in
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- Fig.~\ref{time-evolution}). Typical change of the permittivity
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+ Fig.~\ref{time-evolution}). Typical change in permittivity
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corresponding to each stage is shown in Fig.~\ref{plasma-grid}. It
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reveals the EHP evolution stages during interaction of femtosecond
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laser pulse with the Si NPs.
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@@ -596,7 +596,7 @@ GitHub~\cite{Scattnlay-web} under open source license.
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Fig.~\ref{plasma-grid}(f,j). We stress the nonstationary nature of
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E-field pattern at this stage, whereas there is a simultaneous growth
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of the incident pulse amplitude. This leads to a superposition of ED
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- near-field pattern with that from the Stage 1, resulting in EHP
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+ near-field pattern with that from Stage 1, resulting in EHP
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concentration in the front side of the Si NP. This effect dominates
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for the smallest NP with $R=75$~nm in Fig.~\ref{plasma-grid}(b),
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where ED mode is tuned far away from the resonance (see
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@@ -609,7 +609,7 @@ GitHub~\cite{Scattnlay-web} under open source license.
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When the number of optical cycles is large enough
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($t>20$~\textit{fs}) both ED and MD modes can be exited to the level
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necessary to achieve the stationary intensity pattern corresponding
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- to the Mie-based intensity distribution at the \textit{'Stage~3'}
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+ to the Mie-based intensity distribution at \textit{'Stage~3'}
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(see Fig.~\ref{plasma-grid}(c,g,k)). The EHP density for the most
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volume of NP is still relatively small to affect the EHP evolution,
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but is already high enough to change the local optical properties,
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@@ -623,18 +623,18 @@ GitHub~\cite{Scattnlay-web} under open source license.
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resonant size for $R = 115$~nm the $G_{N_e} < 0$ due to the fact that
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EHP is dominantly localized in the back side of the NP.
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- In other words, due to a quasi-stationary pumping during the Stage~3
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- is superposed with the Stage~1 field pattern, resulting in an
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+ In other words, due to a quasi-stationary pumping during Stage~3,
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+ it is superposed with Stage~1 field pattern, resulting in an
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additional EHP localized in the front side. This can be seen when
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- comparing result from the Mie theory in Fig.~\ref{mie-fdtd}(d) and
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- result of full 3D simulation in Fig.~\ref{mie-fdtd}(f). Note that
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+ comparing result from the Mie theory in Fig.~\ref{mie-fdtd}(d) with
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+ that of full 3D simulation in Fig.~\ref{mie-fdtd}(f). Note that
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pumping of NP significantly changes during a single optical cycle,
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- this leads to a large variation of asymmetry factor $G_{N_e}$ at
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- first stage. This variation steadily decrease as it goes to Stage~3,
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+ this leads to a large variation of asymmetry factor $G_{N_e}$ at the
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+ first stage. This variation steadily decreases as it goes to Stage~3,
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as shown in Fig.~\ref{time-evolution}(b,d,f).
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To explain this effect, we consider the time evolution of average EHP
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- densities $N_e$ in the front and back halves of NP presented in
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+ densities $N_e$ in the front and back halves of the NP presented in
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Fig.~\ref{time-evolution}(a,c,e). As soon as the recombination and
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diffusion processes are negligible at \textit{fs} time scale, both
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$N_e^{front}$ and $N_e^{back}$ curves experience monotonous behavior
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@@ -642,14 +642,14 @@ GitHub~\cite{Scattnlay-web} under open source license.
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the back halves of NP are separated in space, which obviously leads
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to the presence of time delay between pumping steps in each curve
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caused by the same optical cycle of the incident wave. This delay
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- causes a large asymmetry factor during first stage. However, as soon
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- as average EHP density increases the relative contribution of this
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+ causes a large asymmetry factor during the first stage. However, as soon
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+ as average EHP density increases, the relative contribution of these
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pumping steps to the resulting asymmetry becomes smaller. This way
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variations of asymmetry $G_{N_e}$ synced with the period of incident
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- light decreases.
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+ light decrease.
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Higher excitation conditions are followed by larger values of
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- electric field amplitude, which lead to the appearance of high EHP
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+ electric field amplitude, which leads to the appearance of high EHP
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densities causing a significant change in the optical properties of
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silicon according to the equations (\ref{Index}). From the Mie
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theory, the initial (at the end of Stage~3) spatial pattern of the
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@@ -666,9 +666,9 @@ GitHub~\cite{Scattnlay-web} under open source license.
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result of multipole modes superposition at the end of Stage~3 and is
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quite different as we change the size of NP. For $R=75$~nm and
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$R=100$~nm, we observe a front side asymmetry before Stage~4,
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- however, the origin of it is quite different. The $R=75$~nm NP is out
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+ however, its origin is quite different. The $R=75$~nm NP is out
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of resonance, moreover, Mie field pattern and the one, which comes
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- from the Stage~1 are quite similar. As soon as EHP density becomes
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+ from Stage~1 are quite similar. As soon as EHP density becomes
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high enough to change optical properties, the NP is still out of
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resonance, however, the presence of EHP increases absorption in
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agreement with (\ref{Index}), decreases Q-factor, and destroys
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@@ -687,7 +687,7 @@ GitHub~\cite{Scattnlay-web} under open source license.
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mark.
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The last NP with $R=115$~nm shows the most complex behavior during
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- the Stage~4. The superposition of Mie-like E-field pattern with that
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+ Stage~4. The superposition of Mie-like E-field pattern with that
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from Stage~1 results in the presence of two EHP spatial maxima, back
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and front shifted. They serve as starting seeds for the EHP
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formation, and an interplay between them forms a complex behavior of
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@@ -834,8 +834,8 @@ GitHub~\cite{Scattnlay-web} under open source license.
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knowledge. As a result of the presented self-consistent nonlinear
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calculations, we have obtained spatio-temporal EHP evolution inside
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the NPs and investigated the asymmetry of the EHP distributions. We
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- have revealed EHP strong asymmetric distribution during first optical
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- cycles for different sizes. The highest average EHP asymmetry has
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+ have revealed EHP strong asymmetric distribution during the first optical
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+ cycle for different sizes. The highest average EHP asymmetry has
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been observed for NPs of smaller sizes below the first magnetic
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dipole resonance, when EHP is concentrated in the front side mostly
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during the laser pulse absorption. Essentially different EHP
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