All Questions
16
questions
1
vote
1
answer
40
views
Can an optical medium be lossless and dispersive?
Occasionally, I come across the phrase "lossless dispersive linear optical medium". How can such a medium be possible mathematically? I mean the real and imaginary parts of the electric ...
- 437
1
vote
0
answers
104
views
The speed of light in medium with different frequency
We know that the speed of light in vaccuum can be expressed as $c=\frac{1}{\sqrt{\mu_0\epsilon_0}}$ and thus the speed of light in vaccuum is thus $$v=\frac{1}{\sqrt{\mu\epsilon}}=\frac{c}{\sqrt{\...
- 83
1
vote
1
answer
55
views
Guided waves: showing geometrically that $v_p v_g = c^2$
In griffith's introduction to electrodynamics p.430 there's a Figure 9.25 of the wavefronts. I'm wondering if we can show geometrically $v_p v_g = c^2$ using this kind of figure. I think so, but I can'...
- 37
4
votes
3
answers
244
views
Can a fibre preserve the shape of the light being transported through it?
Can some fibres retain the shape of the light being transported through them?
If I emit radiation towards a sample (in the shape of an "S") and this is reflected back into a fibre, will the ...
- 753
2
votes
1
answer
424
views
Why is a cavity's free spectral range determined by the group refractive index?
Many sources including Wikipedia and others give the free spectral range of a resonator as a function of the group refractive index $n_g$ by
$$ \Delta \nu_{FSR} = \frac{c}{2 n_g L}. $$
I have a hard ...
- 23
1
vote
2
answers
907
views
Phase velocity, Group velocity and group velocity dispersion (GVD)
I'm studying what happens to a wave packet if it propagates in a medium under linear optics conditions. In my equations I have the wave vector $k=\frac{\omega}{c}n(\omega)$ (often called $\beta$) ...
- 11
1
vote
3
answers
262
views
Zero-dispersion wavelength
Please help me understanding the zero-dispersion wavelength in fibers.
I found this wiki-article on the topic. Accordingly:
"In a single-mode optical fiber, the zero-dispersion wavelength is the ...
- 113
-1
votes
1
answer
53
views
Confusion on the indice of refraction: is it dependent on the frequency or not? [duplicate]
I saw in my course than when light hit a medium, it makes some dipole oscillating with the same frequency as the one of the light $\omega$. By a classical mechanics reasoning, one can show that the ...
- 183
0
votes
0
answers
696
views
Dispersion, refractive index against frequency graph
From Hecht optics page 74, the plot of $n$ , the refractive index, against $\omega$ , the angular frequency of the incoming wave is
And the relation between $n$ and $\omega$ is:
Where each $\omega_{...
- 753
1
vote
2
answers
358
views
What does it mean to say that glass has refractive index 1.5?
The refractive index of a material depends on the wavelength of the light incident upon it which is why dispersion happens. When we say that glass has refractive index 1.5 which wavelength do we have ...
- 11.8k
311
votes
2
answers
30k
views
What is Chirped Pulse Amplification, and why is it important enough to warrant a Nobel Prize?
The 2018 Nobel Prize in Physics was awarded recently, with half going to Arthur Ashkin for his work on optical tweezers and half going to Gérard Mourou and Donna Strickland for developing a technique ...
- 134k
1
vote
1
answer
2k
views
Why is the speed of light the same for all colors in a vacuum but different depending on the color when light goes through a non-air medium? [duplicate]
I know that red light travels faster in non-air mediums than blue light because of its wavelength, but I'm not understanding why this doesn't happen in a vacuum? This is related to the topic of ...
- 33
0
votes
0
answers
95
views
What is the physical origin of group velocity dispersion? [duplicate]
Group velocity dispersion is the phenomenon that the group velocity of light in a transparent medium depends on the optical frequency or wavelength. [quoted from wiki]. I have tried to do my research, ...
- 1,239
0
votes
1
answer
291
views
Wave propagation in gyrotropic medium
Given a gyrotropic material with
$$\vec D = \epsilon \vec E + \lambda / c \vec H \\ \vec B = v / c \vec E + \mu \vec H$$
where $\epsilon, \lambda, v, c, \mu$ are constants (no relation ...
- 196
2
votes
1
answer
2k
views
Why does the speed of the Electromagnetic wave in the material depend on the frequency of the wave where as they are constant in vacuum (freespace)? [duplicate]
I am confused on why would the propagation speed of any EM waves at ANY frequency is constant in the free space (vacuum) but they seem to disperse in any other materials as the propagation speed of EM ...
- 155