All Questions
17
questions
0
votes
0
answers
40
views
Can a beam be expanded by Hermite-Gaussian modes having a different waist position?
Hermite-Gaussian modes of propagating beam are expressed as
\begin{equation}
E_{l,m}(x,y,z) = E_0\frac{\omega_0}{\omega(z)}H_l\left(\sqrt{2}\frac{x}{\omega(z)}\right)H_m\left(\sqrt{2}\frac{y}{\omega(z)...
- 11
0
votes
1
answer
56
views
What is the tiny dot of light in front of both lens in the image? I noticed it while trying to pass a 800 nm pulsed laser through the lens setup
The tiny white dots were formed in front of both the lens when I was trying to pass a 7W, 90 fs, 800 nm pulsed laser through the lens setup shown in the image.
I noticed that the dots disappear when I ...
0
votes
3
answers
322
views
Formal proof that stacking multiple polarizers does/does not improve the extinction ratio?
Assume that you have a light source, e.g. a laser diode, with a polarization extinction ratio (ER) of 100:1, and you need to improve the extinction ratio as much as possible by adding polarizers, e.g. ...
- 181
0
votes
0
answers
178
views
Maximum Intensity for Gaussian Beam
So I wanted to find out the maximum intensity for a Gaussian beam for a given aperture $D$ which is valid for near and far field, as a function of distance $z$, wavelength $\lambda$ and initial power $...
1
vote
0
answers
226
views
Which of those two is better way of avoiding mode hopping in laser?
I'm supposed to design a laser cavity that would avoid mode hopping.
I have two projects in mind, and I did some simulations. The result for relative intensity of modes (no gain spectrum in account, ...
- 3,034
0
votes
2
answers
361
views
What is the angular distribution of stimulated emission radiation? Is it zero at 90 degrees?
We're familliar with talking about stimulated emission using energy and time domains (e.g. Wikipedia's Stimulated emission) but what about spatially?
My naive guess is that since the stimulating ...
- 6,273
1
vote
5
answers
416
views
Is there a beating note for a sideband modulated laser beam?
In short: A laser at frequency $\omega$ gets phase-modulated at $\Omega$ (e.g. with an electro-optical modulator), such that the lowest order sidebands appear at $\omega\pm\Omega$. If this laser beam ...
- 97
2
votes
0
answers
76
views
Minimum diameter of electromagnetic beam in terms of wavelength
Is there a limit on the minimum diameter that a collimated electromagnetic beam must have (lasers or masers), in terms of its wavelength, or it is possible to create a beam with its diameter smaller ...
- 31
5
votes
4
answers
2k
views
Can a soap bubble bounce off a laser?
Clip; I presume some momentum transfer's at play, but can't put a full picture together. What's going on - why does the laser 'repel' the bubble? ... or is it fake?
0
votes
1
answer
333
views
Spectral full width at half max of a Gaussian light pulse [closed]
I need to calculate the spectral full width at half max (FWHM) of a Gaussian light pulse.
The frequency spectrum of a Gaussian light pulse is
$$ \tilde{E}(\omega)\propto \exp{-\frac{(\omega-\omega_0)...
- 485
1
vote
3
answers
159
views
What happens to the $E$ and $B$ fields at the edge of a laser beam?
In an ideal plane wave, $E$ and $B$ fields run off to infinity in both directions along straight paths. I've always assumed the center of a laser beam looks like an ideal plane wave, with $E$ and $B$ ...
- 3,407
3
votes
3
answers
1k
views
How can a wavelength be defined for a laser where a photon's travel distance over a pulse duration is less than a wavelength?
Femtosecond laser pulse are widely used in experimental physics. Femtosecond lasers like Nd:YAG systems produce coherent light at wavelength 1053nm. The distance traveled by a photon in 1 fs is 300nm; ...
- 33
1
vote
0
answers
71
views
Laser Basics: Why does gain scale with wavelength to the power of 5
I've read numerous times that the gain cross section for laser materials (e.g. Titanium Sapphire) is proportional to the fluorescence spectrum multiplied by the wavelength to the power of 5.
(e.g. in ...
- 83
5
votes
1
answer
1k
views
Does light from a super continuum laser remain coherent?
Is the broad spectrum light from a super continuum (white) laser system when filtered for a particular wave length still temporally coherent to a similar degree as the source laser?
i.e. Does the ...
- 1,144
1
vote
1
answer
319
views
Birefringent filter, optical path length difference?
In 'The Light Fantastic' by Kenyon, I.R. (p424), it is said that for a birefringent material inclined at Brewster's angle and who's optical axis lies in the plane of the plate, we have an optical path ...
