All Questions
21
questions
1
vote
1
answer
55
views
Permittivity real and imaginary parts with similar value possible?
Here's the context; I'm studying biological tissues that are supposed to behave like dielectrics. Using the modified cole-cole equation for theoretical predictions:
$$\tilde{\varepsilon}_r (\omega )= \...
- 189
2
votes
2
answers
45
views
How should I calculate the TE and TM modes on an anisotropic/uniaxial slab waveguide?
I want to find the equations governing the TE and TM modes on the following three-layered slab waveguide:
I know how to use the Helmholtz equation and solve for the boundary conditions on normal ...
0
votes
1
answer
60
views
Why the dielectric permitivity matrix of lossless media is symmetric?
I am studying optics and I met a strange statement in the section 2.3.4 (page 34) of Fundamentals of Nonlinear Optics by Peter E. Powers and Joseph W. Haus.
The relationship between $\vec{D},\ \vec{E}$...
- 388
0
votes
1
answer
123
views
Wave propagation in inhomogeneous media
There is a problem I'm trying to solve for some time now and is about the standard (?) approximation that it is made when one tries to solve the Helmholtz equation in inhomogeneous media, that is
\...
- 11
1
vote
1
answer
112
views
Where can I find tables of the refractive index (real and complex part) or dielectric function as a function of frequency for different materials?
I need this information to do simulations for my master's thesis but I don't know if there is a bibliography or a repository on the internet with this information. They are simple materials, water, ...
0
votes
1
answer
226
views
Plugging $j= \sigma E$ into Maxwell's equations, but $q = 0$?
In order to derive the dispersion relation for a dielectric material (including the dielectric constant $\epsilon$ and the conductivity $\sigma$), one starts with the macroscopic maxwell equation, i.e....
3
votes
3
answers
895
views
Why is wood opaque?
Glass does not allow the flow of electrons through it, is transparent, and has higher skin depth. Similarly, wood has no free electrons and higher skin depth, but still it is opaque. Why?
- 165
2
votes
1
answer
91
views
Physical interpretation of increasing Reflectivity with increasing $\epsilon_i$ for small $\epsilon_r$
Currently I have plot Reflectivity, $R$ of a generic material (assuming a complex dielectric function, $\epsilon = \epsilon_r + i\epsilon_i$) as a function of $\epsilon_i$ for various $\epsilon_r$ ...
- 123
1
vote
0
answers
288
views
Reflectivity as a function of complex dielectric function - obtaining negative reflectivity values?
This maybe a bit of a silly question of my part, but I am trying to rewrite the Reflectivity, $R$ as a function of the complex dielectric function $\epsilon = \epsilon_r + i\epsilon_i$. Starting from ...
- 123
1
vote
1
answer
543
views
What is the physical reason of anomalous dispersion in Lorentz model?
According to the Lorentz model of dispersion, a dielectric has a bunch of resonant frequencies $\{\omega_{0j}\}$ for $j=1,2,...$.
In a frequency interval around any resonant frequency $\omega_0$, the ...
- 11.8k
1
vote
2
answers
1k
views
Conductivity from dielectric permittivity
If I have a typical Drude dielectric permittivity:
$$\epsilon(\omega) = \epsilon_{\infty} - \frac{\omega_p^2 \tau}{\omega^2\tau + i\omega}$$
Now, decomposing $\Re{(\epsilon(\omega))}$ and $\Im{(\...
- 221
1
vote
1
answer
183
views
Permittivity-Conductivity relationship sign problem
I have asked this question a number of times and am still uneasy with it.
I want to know how somebody can derive the equation (also see above, picture from a publication):
$$\epsilon(\omega)=\...
- 221
0
votes
1
answer
550
views
Whats the frequency of the modes in a waveguide?
I have been able to confuse myself: I am studying the form of the modes in a rectangular waveguide:
I understand that each mode has a different spatial distribution, but what I dont understand is if ...
- 155
2
votes
1
answer
108
views
Electromagnetic irradiation of a dielectric: Transforming the striction force equation
Consider the simple case of electromagnetic irradiation of a homogeneous isotropic dielectric, neglecting the dispersion of the refractive index. Assuming a transparent medium, the spatial density of ...
- 889
0
votes
1
answer
2k
views
Cutoff wave-number in wave-guides
When defining the dispersion relation in a waveguide we have an equation that also includes a cutoff wave-number. This cutoff wave number depends on the geometry of the waveguide.
$$
k_z = \sqrt{\...
