Questions tagged [waveguide]
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199 questions
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Where do signals travel in a coaxial cable?
A quiz question I recently saw essentially states the following:
In an ideal coaxial line, a radiofrequency signal will travel only through the inner conductor.
A coaxial cable can be thought of as ...
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Is it possible for both electric and magnetic fields to have longitudinal component in a rectangular waveguide?
I know a rectangular waveguide cannot support TEM waves, but supports TE and TM waves. In the TE mode, $E_z=0$ and in the TM mode, $H_z=0$ (where propagation direction is along the $z$-axis). I want ...
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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 ...
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Mode propagation constant in optical fibers
$$\beta = k \sqrt{n_1^2 - \left(\frac{m\lambda}{2a}\right)^2}$$
where $m$ is one of the possible modes (from $0$ to $M-1$ where $M$ is no. of guided modes) and $a$ is the diameter of the optical fiber....
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Is there a generalization of mode coupling theory?
I am currently reading a lecture on coupled-modes theory and have a question regarding the ansatz:
$$E_\text{tot}=A(z)E_1(x,y,z) + B(z)E_2(x,y,z) \\ H_\text{tot}=A(z)H_1(x,y,z) + B(z)H_2(x,y,z)$$
and
$...
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Ambiguities in optical waveguide modes
While studying concept of slab waveguide mode, I got stuck on some problems.
In textbook(Yariv chapter 3 pg 112), for guided TE modes it tells that the mode function
is taken as
which means that the ...
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Helmholtz equation in a metal waveguide channel
I have a problem with the concept of solving the Helmholtz equation in a metal waveguide channel. An example in which I encountered a contradiction was that we have a waveguide channel with dimensions ...
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Phasors and propagating modes in a waveguide
I'm currently studying antennas. The notes I'm following, while discussing the EM fields at the antenna feed port, make the following statement:
It can be shown that a propagating mode in a ...
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How to determine the light rays difference according to book by Okamoto?
In the very beginning of the book "Fundamentals of Optical Waveguides" by Okamoto, there is a description of light ray propagation in the waveguide. I provided an updated Figure from it:
...
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How can evenescent coupling work if an evanescent field cannot transport energy?
This youtube video shows a simulation of evanescent coupling between a driven optical fiber and another that is not driven. I had never heard of evanescent fields so I looked it up on Wikipedia, where ...
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How to eliminate polarization mismatch in the Michelson interferometer based on single-mode optical fiber?
We are developing a mobile system for optical coherence tomography based on fiber optic Michelson interferometer. We are facing a problem of chenging the polarization during a movement of the fiber. ...
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Frequency and Wavenumbers in Rectangular Waveguide for TE01
In Chapter 9 of Principles of Electrodynamics by Schwartz, which is on waveguides and cavities, there is an analysis of a simple rectangular guide and a calculation of the lowest frequency that can ...
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Light scattering out of an optical waveguide?
I am trying to understand the concept of waveguiding, scattering, and total internal reflection. I have a question regarding the optical waveguides.
Let's consider an optical waveguide transmitting ...
user390982
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Dielectric wave guides vs metallic wave guides
I have a couples of questions regarding wave guides. First of all, why are dielectric wave guides better than metallic wave guides for wavelengths in the visible spectrum? Also, for non-ideal metallic ...
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Waveguide allowed modes | Transverse resonance condition
Consider a planar waveguide for example. The guiding index is $n_f$, and the cover and substrate indices are $n_c$ and $n_s$ respectively. Let the waveguide propagate along z, and have a height $h$ in ...
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Effective Refractive index of a mode less than that of the cladding refractive index?
Can the effective refractive index be less than the cladding if the waveguide width is very small. For example for the case of a ~100 nm waveguide.
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Why are modes other than TEM not allowed for unguided waves?
I know the argument for why TEM waves are only allowed in not simply connected domains in waveguides. But when talking about unguided waves propagating in the vacuum, in many sources plane waves $E(\...
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Coupled microstrip waveguide: Why do the even and odd modes have different wave velocities?
Why do the odd and even modes in a coupled microstrip waveguide have different phase velocities? Is this also the case for a coplanar strips waveguide?
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Why can't a wave in the cladding of a waveguide phase match to a guided wave?
What is the physical reason behind why a wave in the cladding of a waveguide cannot phase match to a guided wave?
I read that the most common solutions to coupling waves to a guided wave is to use ...
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Circular waveguide excitationfor TE11 coefficients
As we can see below. The theory says that A,B coeffietionts are depending on excitation.
I have simulated a circular waveguide, How do i need to excite my waveguide so i will see the A and B ...
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Method of exciting a special mode in dielectric resonator
A dielctric resonator was constructed in a sandwitch like structure.
The middle layer is saphire er=11.5 ,the top and bottom layers are diamond with er=5.68.
A special mode was excited artifficially ...
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PMC magnetic wall aproximation of a resonator logic
As we can see below, they say that for $TE_{01\delta}$ if a wave hits the border between dielectric constants then it will reflect back so why exactly is this property is PMC (as they say below)
PMC ...
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Recognising magnetic wall and electric walls in circular waveguide mde
by definition magnetic wall is PMC where magnetic field perpendicular to the wall and electric field is parralel to the wall .PEC in the opposite.
In the top photo shown bellow taken from the link ...
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Circular waveguide modes visual difference
As we can see bellow TE01 and TE11 mode taken from the manual bellow.
The fiirence between the two in the first index,but the shape is totally changed.
Is there a logic regarding the shape of the mode ...
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Coupling between field components in waveguides
I've been reading on Jia-Ming Liu's Photonic Devices and I came across this part:
I don't understand the highlighted part: in a TE mode we know that $E_z=0$, but the other components may be non-zero. ...
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How is coupling between different TE modes modelled?
When we bring two waveguides close together we can see some coupling between the modes of the two waveguides and verify energy transfer. Can the same transfer happen in modes within a single waveguide?...
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Could an optical waveguide improve the angular resolution of a telescope?
I have recently learned about the diffraction limit of telescopes that limit their angular resolution. This YouTube video, "Resolving Power of a Telescope" also provides some good background....
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How to derive intrinsic impedance of parallel plate transmission line?
I've been Googling variations of this for hours but I can't seem to find any information on it and the formula my professor provided just seems to come out of nowhere and he provides no explanation or ...
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Is the argument of zero tangential field components in wave guide walls a fallacy? Or: How EM waves "magically" find their correct transverse modes
I just came across a nice answer on Quora, explaining visually how wave guide modes can be constructed from the condition of zero tangential fields in the wave guide walls.
In mathematical terms, this ...
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Difference between solution for Rectangular hollow wave guide and resonant cavity
In Griffith's Introduction to Electrodynamics, he solves for $\vec{E}$ and $\vec{B}$ in a Rectangular waveguide assuming they take the "generic form"
$$\vec{E}(x,y,z,t) = \vec{E_0}(x,y) e^{i(...
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Why does the attenuation constant not affect the wavelength?
Reference: https://en.wikipedia.org/wiki/Propagation_constant#Phase_constant
Let's say I have a propagation constant ($\gamma$), where $jk_z = \gamma = \alpha +j \beta$. Why does the attenuation ...
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Wavelength and propagation constant relation [closed]
Theory
Propagation constant is equal to: $\gamma = j k_z = \alpha + j \beta$
Wavelength: $\lambda = \frac{2 \pi}{Im\{ \gamma \}}$
Wave impedance:
$Z_{TEM} = \frac{\gamma }{ j \omega \epsilon } = \...
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Understanding distant qubit interaction by means of flying particles
Premise: I work on quantum computer science mainly at a circuit level abstraction. During my studies I spent some time to get an understanding of how abstract gates relate to physical settings. My ...
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Guided waves: showing geometrically that $v_p v_g = c^2$
In griffith's introduction to electrodynamics p.430 there's a Figure 9.25 of the wavefronts. I'm wondering if we can show geometrically $v_p v_g = c^2$ using this kind of figure. I think so, but I can'...
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Guided waves $E_z$ and $B_z$
In Griffiths’ Electrodynamics, fourth edition, p.427, we have $$E_x = \frac{i}{(\omega/c)^2 - k^2} \left(k\frac{\partial E_z }{\partial x}+ \omega \frac{\partial B_z}{ \partial y}\right), $$
$$E_y = \...
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TE and TM modes vs polarization
I have often seen people informally (and sometimes formally) refer to TE and TM modes interchangeably with polarization. I don't see how these modes are related to polarization.
Here is what I think ...
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Total Energy of an Asymetric 3x3 Coupler
In our experiments, we are using a 3×3 fibre couplers with light as part of an interferometer-setup. This coupler isn't symmetric; it's phase relation of every output is unequal to 120° and the ...
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How do signals propagate down unballanced coaxial transmission lines?
I have previously asked a related question however it was closed, thus I have sorted out my thoughts into this revised question. This new question comes in two parts.
I do not understand the concept ...
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Question about fiber to chip coupling in silicon photonics
I asked a similar question earlier (How is the fiber alignment done in pluggable optical transceiver module (e.g., QSFP-DD)?), but few things are still not clear to me, so I'm posting another one here....
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Why is TE mode preferred to TM mode in the optical waveguide in silicon photonics?
I recently started learning about silicon photonics, focusing on its usage in the high-speed interconnect.
Most papers I've been reading so far use optical waveguides choosing TE00 as the dominant ...
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Spatial distribution for intensity
The paper Evanescently coupled multimode spiral spectrometer describes a novel approach to designing a spectrometer based on a waveguide. When I approached the authors with a question about the theory ...
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How do I know whether waveguides support TE or TM modes?
I'm working through the formalism of waveguides, and I've seen many different situations with various boundary conditions: hollow metal rectangular waveguide, dielectric slab, dielectric rectangular ...
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Confinement of electromagnetic field in coaxial cable
I wonder about the situation when we apply AC voltage or RF voltage on coaxial cable. Typically, the lateral dimension of coaxial cable is smaller than the wavelength of electromagnetic field in such ...
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Two Dimensional Hodge Decomposition
In deriving the equation governing propagation of wave in a wave guide, a specific form of Hodge decomposition theorem is used. The Hodge decomposition theorem applied in two dimensions allows us to ...
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Why do we use wires/conductors to transport energy?
I am currently studying Maxwell equations and I learned that copper wires are essentially just wave guides for EM waves. Why do we not use an insulator to guide the wave and transport the energy which ...
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How are the Boundary conditions for wave guides derived?
So I understand that for a linear material we get the equations where 1 is the material above a boundary and 2 is the new material below the boundary. $$E_1^{\parallel} - E_2^{\parallel} = 0 $$
$$\...
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TEM waves in waveguides and free space
I have seen the mathematical explanation as to why TEM waves cannot exist in hollow waveguides (eg: https://www.youtube.com/watch?v=G8u2WEBF7MY), But that derivation holds good for plane waves in free ...
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Why is the curl of electric field vector inside a hollow waveguide zero for TEM waves?
I have been studying David Griffiths 'Introduction to Electrodynamics', Electromagnetic Waves chapter. For hollow wave guide, the Maxwell's equations
$$\begin{align}
\nabla\cdot\mathbf E &= 0 \\
\...
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Steven Weinberg says $L$ is the fundamental EM wavelength in a cubical cavity $L^3;$ not the typically asserted $2L.$
This is from Steven Weinberg's Lectures on Quantum Mechanics, 2nd Ed., page 2:
For instance, for a cubical box of width $L,$ whatever boundary condition is satisfied on one face of the box must be ...
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How is certain area of waveguide becomes visible to user?
I was reading an article and came across this image
As shown, image becomes visible
to eye after reaching a specific area of the glass. But how does it work? Why is it being reflected at such a weird ...
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