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@@ -450,7 +450,7 @@ Mie theory~\cite{Bohren1983}. It is only valid in the absence of
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nonlinear optical response, thus we can compare it against
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above-mentioned FDTD-EHP model only for small plasma densities, where
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we can neglect EHP impact to the refractive index. Non-stationary
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-nature of a femtosecond pulse increase the complexity of the
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+nature of a~\textit{fs} pulse increase the complexity of the
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analysis. A detailed discussion on the relation between Mie theory and
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FDTD-EHP model will be provided in the next section.
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@@ -524,12 +524,12 @@ license.
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oscillations inside the Si NP. Further on we present transient
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analysis, which reveals much more details.
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- To achieve a quantative description for evolution of the EHP
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+ To achieve a quantitative description for evolution of the EHP
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distribution during the \textit{fs} pulse, we introduced another
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asymmetry factor
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$G_{N_e} = (N_e^{front}-N_e^{back})/(N_e^{front}+N_e^{back})$
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indicating the relationship between the average EHP densities in the
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- front and in the back halfs of the NP. This way, $G_{N_e} = 0$
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+ front and in the back halves of the NP. This way, $G_{N_e} = 0$
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corresponds to the quasi-homogeneous case and the assumption of the
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NP homogeneous EHP distribution can be made to investigate the
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optical response of the excited Si NP. When $G_{N_e}$ significantly
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@@ -542,7 +542,7 @@ license.
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Fig.~\ref{plasma-grid}. For better visual representation of time
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scale of a single optical cycle we put a
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squared electric field profile on all plots in
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- Fig.~\ref{time-evolution} in gray color as a backgroud image (note
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+ Fig.~\ref{time-evolution} in gray color as a background image (note
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linear time scale on the left column and logarithmic scale on the
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right one).
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@@ -582,13 +582,13 @@ license.
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Fig.~\ref{plasma-grid}(f,j). We would like to stress the
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unstationery nature of field pattern at this stage. The energy
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balance between extinction and pumping is not set, moreover, there is
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- a simultaneous growth of the incident pulse apmlitude. This leads to
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+ a simultaneous growth of the incident pulse amplitude. This leads to
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a superposition of ED field pattern with the one from the Stage 1,
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resulting into the presence for the maximum of the EHP distribution
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in the front side of the Si NP. This effect dominates for the
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smallest NP with $R=75$~nm in Fig.~\ref{plasma-grid}(b), where ED
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mode is tuned far away from the resonance (see Fig.~\ref{mie-fdtd}(c)
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- for field supression inside of NP predicted by Mie theory). At this
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+ for field suppression inside of NP predicted by Mie theory). At this
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stage, the density of EHP ($N_e < 10^{20}$~cm$^2$) is still not high
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enough to significantly affect the optical properties of the NP.
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@@ -608,36 +608,36 @@ license.
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the MD resonant size for $R = 115$~nm the $G_{N_e} < 0$ due to
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the fact that EHP is dominantly localized in the back side of the NP.
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- Once again, due to presence of continous pumping the Stage~3 is
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+ Once again, due to presence of continuous pumping the Stage~3 is
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superposed with Stage~1 field pattern, resulting in the additional
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EHP localized in the front side. This can be seen when comparing
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result from the Mie theory in Fig.~\ref{mie-fdtd}(d) and result of
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full 3D simulation in Fig.~\ref{mie-fdtd}(f). Note that pumping of NP
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significantly changes during a single optical cycle, this leads to a
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large variation of asymmetry factor $G_{N_e}$ at first stage. This
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- variation stedialy decrease as it goes to Stage~3.
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+ variation steadily decrease as it goes to Stage~3.
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The explain this we need to consider time evolution of mean EHP
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- densities $N_e$ in the front and back halfs of NP presented in
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+ densities $N_e$ in the front and back halves of NP presented in
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Fig.~\ref{time-evolution}(a,c,e). As soon as 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 behaviour
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+ $N_e^{front}$ and $N_e^{back}$ curves experience monotonous behavior
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with small pumping steps synced to the incident pulse. Front and back
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- halfs are separated in space, wich obviously leads to the presence of
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- time delay between puping steps in each curve caused with the same
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+ halves are separated in space, which obviously leads to the presence of
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+ time delay between pumping steps in each curve caused with the same
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optical cycle of the incident wave. This delay causes a large value
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- of the assymetry factor during first stage. However, as soon as mean
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+ of the asymmetry factor during first stage. However, as soon as mean
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EHP density increases the contribution of this pumping steps to
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- resulting assymetry becomes smallar and the synced with the period of
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+ resulting asymmetry becomes smaller and the synced with the period of
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incident light variation of $G_{N_e}$ decreases.
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Higher excitation conditions are followed with large values of
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- electric field amplitude, which lead to apperance of high EHP
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+ electric field amplitude, which lead to appearance of high EHP
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densities causing a significant change of optical properties of
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silicon according to the equations (\ref{Index}). As it follows from
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Mie theory the initial (at the end of Stage~3) space pattern of
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optical properties is non-homogeneous. When non-homogeneity of
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- optical properties becomes strong enougth it leads to the
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+ optical properties becomes strong enough it leads to the
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reconfiguration of the electric field inside of NP and vice versa. We
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refer to these strong nonlinear phenomena as \textit{'Stage~4'}. In
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general the reconfiguration of the electric field is obligatory as
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@@ -651,7 +651,7 @@ license.
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the origin of it is quite different. The $R=75$~nm NP is out of
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resonance, moreover, Mie field pattern and the one which comes from
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Stage~1 are quite similar. As soon as EHP density becomes high enough
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- to change optical properties the NP is still out of resonanse,
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+ to change optical properties the NP is still out of resonance,
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however, presence of EHP increases absorption in accordance with
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(\ref{Index}). This effectively leads to a kind of screening, it
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becomes harder for incident wave to penetrate deep into EHP. Finally,
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@@ -660,22 +660,22 @@ license.
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For $R=100$~nm the evolution during the final stage goes in a
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similar way, with a notable exception regarding MD resonance. As
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- soon as presence of EHP incresases the absorption, it suppresses the
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+ soon as presence of EHP increases the absorption, it suppresses the
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MD resonance with symmetric filed pattern, thus, the asymmetry factor
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- can be increased. This was actualy observed in
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- Fig.~\ref{time-evolution}(d) with a local maxima near 100~\textit{fs}
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+ can be increased. This was actually observed in
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+ Fig.~\ref{time-evolution}(d) with a local maximum near 100~\textit{fs}
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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 field pattern with the one from
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Stage~1 results into the presence of two EHP spatial maxima, back and
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front shifted. They serve to be a starting seed for EHP formation,
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- the interplay between them forms a complex behavior of the assymetry
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+ the interplay between them forms a complex behavior of the asymmetry
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factor curve. Namely, it changes the sign from negative to positive
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and back during the last stage. This numerical result can hardly be
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explained in a simple qualitative manner, it is too complex to
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account all near-field interaction of incident light with two EHP
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- regions inside a single NP. However, it is intersing to note, that in
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+ regions inside a single NP. However, it is interesting to note, that in
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a similar way as it was for $R=100$~nm the increased absorption
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should ruin ED and MD resonances, responsible for the back-shifted
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EHP. As soon as this EHP region is quite visible on the last snapshot
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