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

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

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Appendix I 2 x 2 Matrix formulation for Isotropic Layered Media [Yeh 88] tel-00916300, version 1 - 10 Dec 2013 Let us consider the case of a plane wave incident on an interface between two media with refractive indices n 1 and n 2 respectively. It is know that a part of the incident wave will be transmitted into medium 2 and a part reected back at medium 1. If E i exp [i (ωt − k i .r)], E r exp [i (ωt − k r .r)] and E t exp [i (ωt − k t .r)] are the eld amplitudes of the incident plane wave, reected and transmitted waves respectively, following the boundary conditions all the three propagation vectors k i ,k r and k t must lie in a plane. This plane where the propagation vectors of incident, reected and transmitted wave lie is known as the plane of incidence. In such a plane, the tangential components θ i ,θ r and θ t of the wave vectors with regard to the normal of the plane interface satisfy the following condition, n 1 sinθ i = n 1 sinθ r = n 2 sinθ t Eqn (i) These kinematic properties hold true for many types of propagation vectors such as light waves, sound waves, matter waves etc.,. But, the dynamical properties such as the intensity of the reected and transmitted waves, phase changes and the polarization eect depend on the specic nature of wave propagation and their boundary conditions. Extending the case above to TE polarization in a thin lm with three interfaces at air, thin lm and susbstrate, −→ E (x) for the s wave is a continuous function of x. However when decomposed into the right and left travelling components (Ref. Fig.5.1), they are no longer continuous at the interfaces. The amplitude of the eld at the left and right side of the interface at x = 0 can be represented as column vectors and linked by ( ( A ′ 2 B ′ 2 ( ) ( A 1 = D1 −1 D 2 B 1 )=P 2 ( ) ( A 2 = B 2 ) ( A 2 =D2 −1 D 3 B 2 A ′ 2 B ′ 2 A ′ 3 B ′ 3 )≡ D 12 ( e iφ 2 0 0 e −iφ 2 )≡D 23 ( A ′ 2 B ′ 2 )( A ′ 3 B ′ 3 ) ) A 2 B 2 ) Eqn (ii) Eqn (iii) Eqn (iii) where D 1 ,D 2 and D 3 are the dynamical matrix which relates the refractive index 188

and the tangential components of the wave vectors in medium 1,2 and 3 and is given by, D α = ( ) 1 1 n α cosθ α −n α cosθ α Eqn (iv) tel-00916300, version 1 - 10 Dec 2013 where α = 1, 2, 3 and θ α is the EM wave angle in each of the media which is related to β and k αx by, ω β= n α c sinθ ω α, k αx = n α c cosθ α Eqn (v) P 2 is the propagation matrix which acounts for the propagation of the EM wave through the thickness of the lm and φ 2 is given by k 2x d. The matrices D 12 and D 23 may be regarded as the transmission matrices which link the amplitude of the eld on the two sides of the interfaces as: ⎛ ( 1 1 + k ) ( 2x 1 1 − k ) ⎞ 2x D 12 = ⎜ 2 k 1x 2 k 1x ( ⎝ 1 1 − k ) ( 2x 1 1 + k ) ⎟ 2x ⎠ Eqn (vi) 2 k 1x 2 k 1x ⎛ ( 1 1 + k ) ( 3x 1 1 − k ) ⎞ 3x D 23 = ⎜ 2 k 2x 2 k 2x ( ⎝ 1 1 − k ) ( 3x 1 1 + k ) ⎟ 3x ⎠ 2 k 2x 2 k 2x Similarly in the case ⎛of TM ( polarized ) waves, ( ) ⎞ 1 1 + n2 2k 1x 1 1 − n2 2k 1x D 12 = ⎜ 2 n 2 1k 2x 2 n 2 1k 2x ( ) ( ) ⎟ ⎝ 1 1 − n2 2k 1x 1 1 + n2 2k 1x ⎠ 2 n 2 1k 2x 2 n 2 1k 2x Eqn (vii) Eqn (viii) ⎛ ( ) ( ) ⎞ 1 1 + n2 3k 1x 1 1 − n2 3k 1x D 23 = ⎜ 2 n 2 2k 2x 2 n 2 2k 2x ( ) ( ) ⎟ ⎝ 1 1 − n2 3k 1x 1 1 + n2 3k 1x ⎠ Eqn (ix) 2 n 2 2k 2x 2 n 2 2k 2x The expressions for D 12 and D 23 are similar, except the fact that they are represented by suitable subscripts referring to their corresponding media. D 12 can be formally written as, ( ) D 12 = 1 1 r 12 Eqn (x) t 12 r 12 1 where t 12 and r 12 are the Fresnel transmission and reection coecients given by, r 12 = k 1x − k 2x and r 12 = n2 1k 2x − n 2 2k 2x for s wave and p wave respectivelyEqn k 1x + k 2x n 2 1k 2x + n 2 2k 2x (xi) 189

and the tangential components of the wave vectors in medium 1,2 and 3 and is given<br />

by,<br />

D α =<br />

(<br />

)<br />

1 1<br />

n α cosθ α −n α cosθ α<br />

Eqn (iv)<br />

tel-00916300, version 1 - 10 Dec 2013<br />

where α = 1, 2, 3 and θ α is the EM wave angle in each of the media which is<br />

related to β and k αx by,<br />

ω<br />

β= n α<br />

c sinθ ω<br />

α, k αx = n α<br />

c cosθ α<br />

Eqn (v)<br />

P 2 is the propagation matrix which acounts for the propagation of the EM wave<br />

through the thickness of the lm and φ 2 is given by k 2x d. The matrices D 12 and D 23<br />

may be regar<strong>de</strong>d as the transmission matrices which link the amplitu<strong>de</strong> of the eld<br />

on the two si<strong>de</strong>s of the interfaces as:<br />

⎛ (<br />

1<br />

1 + k ) (<br />

2x 1<br />

1 − k ) ⎞<br />

2x<br />

D 12 = ⎜ 2 k 1x 2 k 1x (<br />

⎝ 1<br />

1 − k ) (<br />

2x 1<br />

1 + k ) ⎟<br />

2x<br />

⎠<br />

Eqn (vi)<br />

2 k 1x 2 k 1x<br />

⎛ (<br />

1<br />

1 + k ) (<br />

3x 1<br />

1 − k ) ⎞<br />

3x<br />

D 23 = ⎜ 2 k 2x 2 k 2x (<br />

⎝ 1<br />

1 − k ) (<br />

3x 1<br />

1 + k ) ⎟<br />

3x<br />

⎠<br />

2 k 2x 2 k 2x<br />

<strong>Si</strong>milarly in the case ⎛of TM ( polarized ) waves, ( ) ⎞<br />

1<br />

1 + n2 2k 1x 1<br />

1 − n2 2k 1x<br />

D 12 = ⎜ 2 n 2 1k 2x 2 n 2 1k 2x ( ) ( ) ⎟<br />

⎝ 1<br />

1 − n2 2k 1x 1<br />

1 + n2 2k 1x<br />

⎠<br />

2 n 2 1k 2x 2 n 2 1k 2x<br />

Eqn (vii)<br />

Eqn (viii)<br />

⎛ ( ) ( ) ⎞<br />

1<br />

1 + n2 3k 1x 1<br />

1 − n2 3k 1x<br />

D 23 = ⎜ 2 n 2 2k 2x 2 n 2 2k 2x ( ) ( ) ⎟<br />

⎝ 1<br />

1 − n2 3k 1x 1<br />

1 + n2 3k 1x<br />

⎠<br />

Eqn (ix)<br />

2 n 2 2k 2x 2 n 2 2k 2x<br />

The expressions for D 12 and D 23 are similar, except the fact that they are represented<br />

by suitable subscripts referring to their corresponding media. D 12 can be<br />

formally written as,<br />

( )<br />

D 12 = 1 1 r 12<br />

Eqn (x)<br />

t 12 r 12 1<br />

where t 12 and r 12 are the Fresnel transmission and reection coecients given<br />

by,<br />

r 12 = k 1x − k 2x<br />

and r 12 = n2 1k 2x − n 2 2k 2x<br />

for s wave and p wave respectivelyEqn<br />

k 1x + k 2x n 2 1k 2x + n 2 2k 2x<br />

(xi)<br />

189

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