文档介绍：Classical propagation
Propagation of light in a dense optical medium
The dipole oscillator model
plex dielectric constant of a dipole
At frequencies close to resonance. Also shown is
The real and imaginary part of the refractive index
Calculated from the dielectric constant.
吸收峰位于o, 半宽= ;
1的极值位于 o ， 1出现负值;
折射率在o 区间出现反常色散。
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The dipole oscillator model
Multiple resonance
Take account of all the transitions in the medium
Schematic diagram of the frequency dependence of the refractive index and absorption of a hypothetical solid from the infrared to the x-ray spectral region. The solid is assummed to have three resonant frequencies with width of each absorption line has been set to 10% of the centre frequency by appropriate choice of the j’s.
Assign a phenomenological oscillator strength
fj to each transition:
For each atom.
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The dipole oscillator model
Comparison with experimental data
Refractive index and (b) extinction co-
Efficient of fused silica (SiO2) glass from the
Infrared to the x-ray spectral region.
1. n >> except near the peaks of the absorption;
2. The transmission range of optical materials is
determined by the electronic absorption in UV
and the vibrational absorption in IR;
3. IR absorption is caused by the vibrational quanta
in SiO2 molecules themselves( 1013 Hz
(21m) and 1013 Hz( m);
4. UV absorption is caused by interband electronic
transition(band gap of about 10 eV), threshold at
2 1013 Hz(150 nm)( ~ 108 m-1);
5. UV absorption departure from Lorentz model;
6. n actually increases with frequency in trans-
parency region, the dispersion originates from
wings of two absorption peaks of UV and IR;
7. The phase velocity of light is greater than c in
region where n falls below unity;
8. Group velocity:
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Local field correction
The dipole oscillator model
Clausius-Mossotti relations