Physical explanation for power broadening

Click For Summary

Discussion Overview

The discussion revolves around the physical explanation for power broadening, particularly how increased decay rates at high intensities lead to a spread of generated frequencies. Participants explore the relationship between excitation, deexcitation, and the implications of wave packet characteristics on frequency distribution.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes the mathematical aspect of saturation leading to increased decay rates but seeks a physical manifestation of this in terms of frequency spread.
  • Another participant suggests that the excitation and deexcitation processes occur over shorter time frames, leading to a broader frequency distribution due to the uncertainty principle related to wave packets.
  • A third participant elaborates on the relationship between the number of cycles in a wave and the precision of frequency definition, indicating that a strongly damped wave or short pulse necessitates a broader range of frequencies.
  • This participant also connects the need for multiple frequencies to create a short wave pulse, emphasizing that a single frequency would require infinite duration.

Areas of Agreement / Disagreement

Participants appear to share an understanding of the relationship between decay rates, wave packet characteristics, and frequency distribution, but the discussion remains exploratory without a definitive consensus on the physical mechanisms involved.

Contextual Notes

Participants reference concepts such as the uncertainty principle and the mathematical relationship between wave characteristics and frequency, but there are no explicit resolutions to the underlying assumptions or mechanisms of power broadening discussed.

Carnot
Messages
18
Reaction score
0
I have been looking into broadening mechanisms and I'm stuck at trying to provide a physical explanation for power broadening. I get how the math shows that at high intenseties the decay rate goes through the roof due to saturation, but how does this increased decay rate manifest in a spread of generated frequencies? Are the electrons reexcited or decaying while between ground and excited states?
 
Physics news on Phys.org
The excitation and deexcitation has "less time". Imagine a wavepacket with a shorter length: it has to have a broader frequency distribution (the mathematical "uncertainty principle" for Fourier transformations). The same happens here.
 
The precision with which you can define the frequency of a wave depends on the number of cycles. If you have 10 cycles, you can define the wave length or frequency to ~10%, 100 cycles to ~1%, 1000 cycles to ~0.1% and so on.

A strongly damped wave or a short pulse has a small number of cycles. A fast decay means strong damping.

Mathematically, in order to produce a short wave pulse you have to overlay waves with many frequencies. The spread of frequencies increases the shorter the pulse. A single frequency wave would have to be infinitely long in space and in time.

(this is the same thing mfb said, in more words)
 
Thank you for both answers, they helped a lot :-)
 

Similar threads

  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 16 ·
Replies
16
Views
4K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 6 ·
Replies
6
Views
7K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 15 ·
Replies
15
Views
3K