Óptica Moderna Fundamentos e aplicações - Fotonica.ifsc.usp.br ...
Óptica Moderna Fundamentos e aplicações - Fotonica.ifsc.usp.br ...
Óptica Moderna Fundamentos e aplicações - Fotonica.ifsc.usp.br ...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
156<<strong>br</strong> />
SA<<strong>br</strong> />
r2a<<strong>br</strong> />
r1a<<strong>br</strong> />
r2b<<strong>br</strong> />
d l<<strong>br</strong> />
P2<<strong>br</strong> />
SB<<strong>br</strong> />
r1b<<strong>br</strong> />
P1<<strong>br</strong> />
r<<strong>br</strong> />
Fig. 7.8 - Fontes pontuais completamente incoerentes.<<strong>br</strong> />
Coerência<<strong>br</strong> />
B<<strong>br</strong> />
Vamos chamar t ′ = t − t1a<<strong>br</strong> />
, t ′′ = t − t1b<<strong>br</strong> />
, t1a<<strong>br</strong> />
− t 2a = τa<<strong>br</strong> />
e t1b<<strong>br</strong> />
− t 2b = τ<<strong>br</strong> />
onde τ e τ são os tempos de coerência transversal de SA<<strong>br</strong> />
e SB. Logo,<<strong>br</strong> />
a<<strong>br</strong> />
b<<strong>br</strong> />
*<<strong>br</strong> />
*<<strong>br</strong> />
*<<strong>br</strong> />
E E E ( t′<<strong>br</strong> />
) E ( t′<<strong>br</strong> />
+ τ ) + E ( t ′′ ) E ( t′<<strong>br</strong> />
′ + τ )<<strong>br</strong> />
1<<strong>br</strong> />
2<<strong>br</strong> />
= (7.27)<<strong>br</strong> />
1a<<strong>br</strong> />
2a<<strong>br</strong> />
a<<strong>br</strong> />
Note que na expressão acima não comparecem os termos<<strong>br</strong> />
E1a<<strong>br</strong> />
E 2b<<strong>br</strong> />
e E 2aE<<strong>br</strong> />
2b<<strong>br</strong> />
, pois as fontes são completamente incoerentes. Apenas<<strong>br</strong> />
os termos diretos não são nulos, isto é,<<strong>br</strong> />
=<<strong>br</strong> />
1<<strong>br</strong> />
2<<strong>br</strong> />
γ<<strong>br</strong> />
(7.29)<<strong>br</strong> />
Logo,<<strong>br</strong> />
1b<<strong>br</strong> />
2b<<strong>br</strong> />
( ) 2<<strong>br</strong> />
*<<strong>br</strong> />
2<<strong>br</strong> />
E E E ( t − t ) + E t − t<<strong>br</strong> />
1<<strong>br</strong> />
1<<strong>br</strong> />
= (7.28.a)<<strong>br</strong> />
1a<<strong>br</strong> />
1a<<strong>br</strong> />
1b<<strong>br</strong> />
b<<strong>br</strong> />
1b<<strong>br</strong> />
( ) 2<<strong>br</strong> />
*<<strong>br</strong> />
2<<strong>br</strong> />
E E E ( t − t ) + E t − t<<strong>br</strong> />
2<<strong>br</strong> />
2<<strong>br</strong> />
= (7.28.b)<<strong>br</strong> />
2a<<strong>br</strong> />
Como as fontes são equivalentes podemos escrever:<<strong>br</strong> />
1 < E<<strong>br</strong> />
=<<strong>br</strong> />
2<<strong>br</strong> />
( t′<<strong>br</strong> />
) E<<strong>br</strong> />
< E<<strong>br</strong> />
( t′<<strong>br</strong> />
+ τ )<<strong>br</strong> />
1a<<strong>br</strong> />
> 1 < E<<strong>br</strong> />
+<<strong>br</strong> />
2<<strong>br</strong> />
2b<<strong>br</strong> />
( t′<<strong>br</strong> />
′ ) E<<strong>br</strong> />
< E<<strong>br</strong> />
* *<<strong>br</strong> />
1a<<strong>br</strong> />
2a<<strong>br</strong> />
a<<strong>br</strong> />
1b<<strong>br</strong> />
2b<<strong>br</strong> />
γ12 2<<strong>br</strong> />
2<<strong>br</strong> />
1a<<strong>br</strong> />
><<strong>br</strong> />
1b<<strong>br</strong> />
1b<<strong>br</strong> />
( t′<<strong>br</strong> />
′ + τb<<strong>br</strong> />
) ><<strong>br</strong> />
><<strong>br</strong> />
a<<strong>br</strong> />
b<<strong>br</strong> />
( τ ) + γ(<<strong>br</strong> />
τ ) = ⎜1−<<strong>br</strong> />
⎟exp(<<strong>br</strong> />
iωτ<<strong>br</strong> />
) + ⎜1−<<strong>br</strong> />
⎟exp(<<strong>br</strong> />
iωτ<<strong>br</strong> />
)<<strong>br</strong> />
a<<strong>br</strong> />
1<<strong>br</strong> />
2<<strong>br</strong> />
b<<strong>br</strong> />
1 ⎛<<strong>br</strong> />
2 ⎜<<strong>br</strong> />
⎝<<strong>br</strong> />
τ<<strong>br</strong> />
τ<<strong>br</strong> />
0<<strong>br</strong> />
⎞<<strong>br</strong> />
⎟<<strong>br</strong> />
⎠<<strong>br</strong> />
a<<strong>br</strong> />
1 ⎛<<strong>br</strong> />
2 ⎜<<strong>br</strong> />
⎝<<strong>br</strong> />
τ<<strong>br</strong> />
τ<<strong>br</strong> />
0<<strong>br</strong> />
⎞<<strong>br</strong> />
⎟<<strong>br</strong> />
⎠<<strong>br</strong> />
[ ω(<<strong>br</strong> />
τ − τ ) ]<<strong>br</strong> />
⎛ τa<<strong>br</strong> />
⎞ 1+<<strong>br</strong> />
cos<<strong>br</strong> />
*<<strong>br</strong> />
a b<<strong>br</strong> />
γ 12 = γ12γ<<strong>br</strong> />
12 =<<strong>br</strong> />
⎜<<strong>br</strong> />
⎜1−<<strong>br</strong> />
⎟<<strong>br</strong> />
(7.30)<<strong>br</strong> />
⎝ τ0<<strong>br</strong> />
⎠ 2<<strong>br</strong> />
S. C. Zilio <strong>Óptica</strong> <strong>Moderna</strong> – <strong>Fundamentos</strong> e Aplicações<<strong>br</strong> />
b<<strong>br</strong> />
b