Films minces à base de Si nanostructuré pour des cellules ...

tel-00916300, version 1 - 10 Dec 2013
1.6 and 2.1). We assume that, there are no losses in the lm due to absorption
and hence set k 2 =0. Figure 5.5 shows the pump prole variation with n 2 , along the
depth (x) from lm surface.
The result indicates that the intensity
of the incident pump and the position
of maxima varies with the refractive
indices of the material. The mean pump
intensity varies monotonously with refractive
index in the three cases investigated
(Tab. 5.5). The lower index resulting
in the highest intensity. The period
of the pump prole also varies with
n 2 . We can thus suppose the variation
of emission intensity with refractive index
is not a sole contribution from Si-np
density, but also the eect of the incident
pump intensity that varies.
Figure 5.5: Pump prole versus real part of
thin lm refractive index (n 2 ).
Real part (n 2 ) of refractive index Pump intensity range W/m 2
1.48 1.4 x 10 4 - 1.5 x 10 5
1.6 1.1 x 10 4 - 9.5x10 4
2.1 2.3 x 10 4 - 7.9 x10 4
Table 5.2: The pump intensity range for the three thicknesses investigated.
(c2) Imaginary part (k 2 ):
In order to investigate the eect of losses, the extinction coecient k 2 of the thin
lm was varied while keeping n 2 xed at 1.6 (Fig. 5.6).
Figure 5.6a shows the pump prole for three cases : k 2 = 0, 0.01 and 0.1 and gure
5.6b illustrates the envelope of the pump maxima and minima taking k 2 = 0.1 as a
typical example. It can be seen from gure 5.6a that there are no losses when k 2 =0
and the intensity of the pump maxima and minima are constant with depth (x).
With increasing values of extinction factor k 2 : (i) the envelopes of the pump maxima
and minima decrease with depth (x) and (ii) the dierence between (Envelope) max.
and (Envelope) min. decreases. This indicates that with increasing losses, the pump
intensity decreases. These factors would inuence the excitation of emitters along
the depth of the thin lm, and consequently on the emission intensity.
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