Questions tagged [photonics]
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96
questions
0
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1answer
19 views
What characterises a rapid delay line?
When reading into Adaptive Sampling for Terahertz Time-Domain Spectroscopy and Imaging, it is stated:
"In general, the advantage of a rapid delay
line is high repetition rate, and the SNR can be ...
1
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2answers
62 views
Need help to prove how equation 2 is obtained from equation 1 (electromagnetism)
Im a undergradute student, and I have little expirience with vector calculus.
Can someone help me to obation equation 2 from equation 1:
where $\vec{k}$ is the wavenumber vector and $\vec{r}$ the ...
0
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1answer
27 views
What happens when a linearly polarised light is incident obliquely on a surface?
I want to know what happens when linearly polarised light is made incident at an oblique angle. In what way the linearly polarised light changes upon reflection.
1
vote
1answer
26 views
Coupling of resonant modes in a 1D Photonic Crystal
In 1D Photonic crystals, a defect can be introduced to create a defect/resonance mode and enable transmission. At first considerations, the thickness of the single defect layer determines the ...
6
votes
1answer
166 views
Homogeneous gain saturation and single-longitudinal-mode lasing
I am currently studying Laser Systems Engineering by Keith Kasunic. Chapter 1.2.1 Temporal Coherence says the following:
Whether or not multiple axial modes will lase depends, in part, on the cavity-...
-2
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2answers
50 views
Diffracted Electrons vs Particulate Electrons (Collapsed): Is there an experimental difference in terms of Double Slits and/or Which Way information? [closed]
In this community, it has been accepted that electrons can self-interfere.
Can an electron interact with itself to create interference?
This video is a good lecture on diffraction gratings and plane ...
0
votes
1answer
35 views
If most types of practical lasers produce a large number of half-wavelengths, then how are they practical for use at all?
I am currently studying Laser Systems Engineering by Keith Kasunic. Chapter 1.2.1 Temporal Coherence says the following:
Axial (or longitudinal) modes are determined by the geometrical fit (or ...
0
votes
1answer
35 views
What software / methods to learn for nanophotonics (a branch of photonics) applications?
I'm new to nanophotonics and been looking for some software and methods (Design, modelling, simulation .etc) used in this scientific field. I'll be grateful to know some.
1
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1answer
26 views
Half-wavelengths of the electric field fit in the cavity length $L$: $m \frac{\lambda}{2n} = L$
I am currently studying Laser Systems Engineering by Keith Kasunic. Chapter 1.2.1 Temporal Coherence says the following:
Axial (or longitudinal) modes are determined by the geometrical fit (or ...
1
vote
1answer
28 views
What are the affects of a beamsplitter on the beam itself (if any)?
I am currently studying the textbook Laser Systems Engineering by Keith Kasunic, and I came across the following diagram:
I understand what a beamsplitter does, but what affect does this splitting of ...
0
votes
1answer
50 views
What is $[\mathrm{J}]$ supposed to denote in this case?
I am currently studying Laser Systems Engineering by Keith Kasunic. Chapter 1.2 Laser Engineering says the following:
If the energy of the incident electromagnetic field more-or-less matches that of ...
0
votes
1answer
18 views
What is the meaning of a finite transverse extent?
In the book Terahertz Spectroscopy and Imaging it is stated that:
"We begin by assuming quasi-collimated propagation of a monochromatic and
spatially coherent beam. Such a paraxial beam travels ...
0
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0answers
16 views
Symplectic Matrix for the Polarizing Beamsplitter Gaussian Unitary Transformation
I would like to use the symplectic matrix for the polarizing beamsplitter's gaussian unitary transformation on the covariance matrix of the two-mode squeezed vacuum state. I have the appropriate ...
0
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1answer
22 views
Ti:Sapphire Laser/Regenerative Amplifier Construction [closed]
I'm interested in exploring air breakdown in the femtosecond regime.
I'd like to generate a beam with a pulse-width of <30fs, with a peak intensity of around 0.5-1mJ/pulse, a repetition rate of at ...
0
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0answers
24 views
Does Hong-Ou-Mandel dip mean anti-correlation?
When entangled photon which is generated by the SPDC process meet together on 50/50 beam-splitter, they are bunching toward either detector D1 or D2. It leads to see the HOM dip which is non-...
0
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0answers
31 views
What is the meaning of the “temporal response” of a system?
This definition of temporal response states that:
"Characteristic of deflected light power defined as the quadratic invariant function of the video signal amplitude."
I don't quite ...
1
vote
1answer
52 views
Spin of quasiparticle formed by photon in glass
This previous question about the effective mass of a photon traveling through glass has a few answers that say we can think of it as a quasiparticle with an effective mass. Photons are spin-1, but ...
0
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0answers
25 views
Can you explain Vernier effect in fairly simple terms?
I already searched myself, but none of the sources I found explains it in itself. Usually it's some paper that uses Vernier effect for something. It's all convoluted. All I understand is that non-...
0
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0answers
17 views
What is the light line or light cone and how is related with total internal reflection and snell law?
I'm have been reading about light propagation in periodic dielectrics. And in one part they introduce the light line. They mention that whenever the parallel and vertical components of the wave vector ...
0
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0answers
13 views
Simple method for calculating and plotting the band structure of a known periodic potential?
A thousand pardons if this is trivial, but I've been stuck here for hours.
I'm trying to compute the spectrum and eigenfunctions (i.e. band structure) of the eigenvalue equation $u'' + k^2\epsilon\...
0
votes
2answers
39 views
What is the importance of a high modulation depth?
I understand that the modulation depth of a sinusoidally modulated signal can be defined as the modulation amplitude divided by the mean value, as explained here.
But why would one wish for a high ...
0
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1answer
23 views
How does photonic propulsion work? [closed]
I just heard about the photonic propulsion and it looks like light may have a mass ! Which is known by the name of "relative mass".
The question is way too generic but here are more ...
1
vote
0answers
15 views
What is the physical meaning behind negative slope of laser characteristics?
Sometimes I measure LIV curves of many semiconductor lasers with the same material and width and different cavity length.
There should be positive slope and intercept of Threshold current vs inverse ...
0
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0answers
14 views
What distribution shape does this broadband signal have if the bandwidth changes?
In the Lumerical tool, I'm simulating a setup using a broadband dipole signal. It is (or should be) centered at $\lambda=$ 922.5 nm and has various bandwidths $\Delta \lambda$ for different ...
1
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0answers
56 views
How do single-pixel cameras work?
To obtain images using a single-pixel camera we need a Digital Micromirror Device (DMD) because single-pixel cameras only possess a single detector (article).
From my understanding, a single-pixel ...
1
vote
1answer
25 views
What are extended modes?
What are extended modes?
I came across this concept while reading about photonics and photonic crystal. But I am not sure what is an extended mode.
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0answers
10 views
Is characteristic temperature $T_0$ of a semiconductor laser geometry independent?
Can I compare $T_0$ of one laser to another one, with different length and width?
For example, let's say there are two lasers:
Laser A
Width: 20 $\mu m$
Length: 500 $\mu m$
$T_0$: X
Laser B
Width: ...
0
votes
2answers
30 views
Ghosting/Unwanted refection with cube beam splitter
I am new in working with an optical setup. I have a small setup to mimic a 3D printer motion stage.
So, it consists of a laser hitting on a cube beam splitter. The transmitted one is dumped while the ...
0
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0answers
25 views
How does a Rib Waveguide has TM00 and TE00 Modes?
For rectangular waveguide, TE00 and TM00 modes cannot exist. However, in one of the research papers they have used TE00 and TM00 modes of Rib Waveguide. I am unaware of the differences between ...
2
votes
4answers
106 views
Is it possible to transfer light between two elements at a distance closer than the wavelength of the light?
Let's say we have a nanoscale laser or led(5nm width/length/height) emitting photons(red, 650nm wavelength) in a direction parallel to its plane, then at 20nm distance in the direction of the emission ...
0
votes
1answer
13 views
What is the formal definition of Coupling efficiency
Does anyone knows the formal definition of Coupling efficiency?
I have been reading the term in photonics devices and optics.
I have been searching for it, but I could not find any.
Thanks for the ...
0
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0answers
29 views
For whispering gallery modes with $n$ nodes, why do the $z$- and $x$-polarized electric fields have $n$ and $n-2$ nodes respectively?
I am analyzing a GaAs nanowire with a length of 2 microns on a GaAs substrate. I am interested in the modal analysis of whispering gallery modes; modes that - through a combination of total internal ...
0
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1answer
20 views
Does self-phase modulation generate new frequency components?
Not a physicist. Hope to clarify some conceptual issues I have with non-linear propagation of light through a medium, since I seem to be mixing up some very fundamental concepts. Specifically, I am ...
0
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0answers
26 views
Variational principle electromagnetism
In the following text of the picture, it says that the numerator is minimized if the spatial oscillation of the electrical field are minimized too. I don't understand why is this the case.
Someone ...
1
vote
3answers
89 views
A single spatial mode whose associated harmonic oscillator is in its $n$th excited state unambiguously contains $n$ photons?
I am reading the introduction to the textbook The Quantum Theory of Light, third edition, by Louden. When discussing the photon, the author says the following:
The idea of the photon is most easily ...
2
votes
2answers
91 views
Scattering vs Stimulated Emission
I am currently reading Practical Flow Cytometry, fourth edition, by Howard M. Shapiro. The author says the following when discussing scattering:
Scattering, which explains both reflection and ...
1
vote
2answers
56 views
What “adiabatic” means in context of photonic waveguides?
I only know the thermodynamic definition that "adiabatic process is a process that doesn't exchange the heat or mass with the surroundings".
Does it mean, that for example "adiabatic ...
0
votes
2answers
40 views
In the end, how do I make a semiconductor laser with specific wavelength?
I know that laser wavelength depends on four important properties:
Bandgap of its material
Gain spectrum
Length of cavity
Size of a quantum well, if we talk about the quantum well laser
But it's a ...
1
vote
2answers
27 views
How thin can a layer be in a multilayer and still act as a reflection interface?
Assume a multilayer with high and low refractive index layers. Now imagine that the high refractive index layers are successively made thinner and thinner. At what point would a single layer no longer ...
0
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0answers
6 views
Can a lens based on grating couplers with an optical tap be made in standard silicon photonics (>120nm sizes)?
Given standard silicon photonic feature limits (say no finer than 120nm), am I right in thinking that it's not very feasible to create a low loss vertical grating based lens that also can tap a ...
0
votes
1answer
39 views
Imaging with two lenses: what if the distance between the lenses is not 2f?
A $4F$-configuration is usually utilized for imaging with $2$ lenses. An object is placed in the focus of the first lens ($f_{1}$), then the second lens is located at a distance $f_{1}+f_{2}$ from the ...
0
votes
1answer
64 views
Understanding guided and non-guided modes in a waveguide
Usually, an optical waveguide is considered in the following way. We have a plane wave traveling inside the waveguide at a certain angle $\alpha$ (which corresponds to the direction of the wavevector $...
1
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0answers
69 views
Will the Airy pattern be preserved for high numerical aperture lens?
All we know that a lens focuses a plane wave into an Airy pattern distribution. However, what if the numerical aperture ($NA$) will be very high, like more than $0.99$ (in the air) or with focusing ...
0
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0answers
24 views
What are some of the applications of Helium-Neon lasers?
I've worked with them in the lab and while they have a very nice Gaussian beam profile, they are tedious to say the least to align(2 hours to align a HeNe laser compared with 5 minutes to align a ...
1
vote
1answer
47 views
Confusion in understanding the Lambertian law
Lambertian law states that the luminous intensity of light emitted from a perfectly diffusing surface is proportional to the $cos(\theta)$ between the surface normal and the direction of observation. ...
0
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4answers
65 views
Doppler shifts appear to violate conservation of energy
If the relative distance between an infrared source and a spectrometer is shortening at a such a rate that the spectrometer detects that radiation at a Doppler- (or blue-) shifted wavelength in the UV ...
0
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1answer
98 views
Why does the focusing efficiency drop with numerical aperture for a microscope objective?
I am doing the following experiment in my lab. I have a collimated laser beam, which is focused by a lens. Then the light is collected by a microscope objective. Also, I use two lenses (L1 and L2) to ...
0
votes
1answer
21 views
Solid-state lasers: The peak power of each pulse is at least three orders of magnitude above the average output power?
My textbook, Solid-State Laser Engineering, 6th edition, by Walter Koechner, says the following:
Average Output Power. The majority of solid-state lasers available commercially have output powers ...
1
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2answers
123 views
Fourier Optics - Impulse Response of Free Space from Fresnel Transfer Function
I am currently reading the chapter "Fourier Optics" in the book "Fundamentals of Photonics" by Saleh and Teich. However I am not able to follow one specific mathematical derivation.
On page 111 the ...
2
votes
0answers
73 views
Stark level manifold
In this figure from https://www.rp-photonics.com/effective_transition_cross_sections.html:
When a high energy photon (920nm) is absorbed followed by phonon emission to lower energy level in the ...
