Ultrashort Laser Pulse Phenomena, 2nd Edition

42 Fundamentals

At given material parameters and carrier frequency, shorter pulses always lead

to a dominant pulse spreading. For T

2

= 10

−10

s (typical value for a single

electronic resonance), and a detuning ωT

2

= 10

4

, we find for example:

τ

rel

W

rel

≈ W

rel



1200 fs

τ

G0



4

. (1.163)

To summarize, a resonant transition of certain spectral width 1/T

2

influences short

pulse (pulse duration < 1ps) propagation outside resonance mainly because of

dispersion. Therefore, the consideration of a transparent material (

i

≈ 0) with

a frequency dependent, real dielectric constant (), which was necessary to

derive Eq. (1.93), is justified in many practical cases involving ...