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现代光电子学(2)

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国家自然科学基金委员会<br />

数理学部实验物理讲习班<br />

导带自由电子在单色电磁场作用下的运动方程<br />

介电常数<br />

ω<br />

2<br />

dr dr<br />

γ 2<br />

dt dt<br />

m + m =−eE<br />

e<br />

0<br />

−iωt<br />

2 2 2<br />

ωp ωp ωγ p<br />

εω ( ) = 1− = 1−<br />

+ i<br />

2 2 2 2 2<br />

ω + iγω<br />

ω + γ ωω ( + γ )<br />

p<br />

当ω >> γ时<br />

1<br />

2 2<br />

⎛ ne ⎞<br />

= ⎜ ⎟<br />

⎝ε0m⎠ (特鲁德)等离子体频率<br />

ω<br />

2<br />

p<br />

1( ) ≈1− 2<br />

ε ω<br />

ω<br />

ω = ω p时,ε 1(ω) = 0<br />

2<br />

ωp<br />

ε2( ω) ≈ γ 3<br />

ω

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