非线性光学讲稿(4)
非线性光学讲稿(4)
非线性光学讲稿(4)
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1<br />
2<br />
2<br />
2ω<br />
( ω)<br />
n(<br />
2ω<br />
) ε<br />
2<br />
因光强 I = ε0cn<br />
E 故→<br />
国家自然科学基金委员会<br />
数理学部实验物理讲习班<br />
2<br />
I2 ( L)<br />
=<br />
d<br />
3 2<br />
eff<br />
c n<br />
0<br />
[ I<br />
1<br />
( 0)]<br />
2<br />
L<br />
2<br />
2<br />
sin ( ΔkL<br />
/ 2)<br />
2<br />
( ΔkL<br />
/ 2)<br />
100<br />
(4.18)<br />
L -作用长度 I1( 0)<br />
-基频光的光强<br />
因光功率 S = IA ( A 为光束截面),故倍频效率为:<br />
S(<br />
2ω<br />
)<br />
2ω<br />
S(<br />
ω)<br />
( ΔkL<br />
/ 2)<br />
2<br />
2<br />
η =<br />
S(<br />
ω)<br />
2<br />
=<br />
d<br />
3 2<br />
eff<br />
c n ( ω)<br />
n(<br />
2ω<br />
) ε0<br />
A<br />
2<br />
L<br />
2<br />
( ΔkL<br />
/ 2)<br />
(4.19)<br />
Δk = 0 →<br />
2<br />
2ω<br />
2<br />
η max =<br />
d<br />
3 2<br />
eff<br />
c n ( ω)<br />
n(<br />
2ω<br />
) ε0<br />
S(<br />
ω)<br />
2<br />
L<br />
A<br />
sin<br />
★基频振幅不能看作恒量:若 = 0则<br />
(4.15)和(4.16)→ d iω<br />
2<br />
Δk n ( 2ω)<br />
= n(<br />
ω)<br />
= n<br />
E ρ<br />
E 2 = deff<br />
E1<br />
dz cn<br />
E 2 = iρ2<br />
D deff<br />
cn<br />
dE1<br />
iω<br />
∗<br />
= deff<br />
E2E1<br />
dz cn<br />
ω<br />
= →<br />
令: 1 = 1