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Is it possible to laser cool without using spatially-varying magnetic fields and above zero degrees?
is it possible to laser cool without generating a weak quadrupolar magnetic field?
Yes. Optical molasses cooling does not require any magnetic fields. But there is nothing providing a restoring force and hence "trapping"$^\dagger$. Experimentally, you usually first do a MOT and then an optical molasses stage.
is it possible to use laser cooling ...
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The key point is that a laser beam is a wave which propagates according to Huygens principle. Once you accept this fact the divergence follows naturally.
Huygens principle states that the propagation is due to the generation of spherical waves, which will generate spherical waves in the next step of propagation. [Picture taken from wiki]
In the image we see ...
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Composites are placed while still in a soft, dough-like state, but
when exposed to light of a certain blue wavelength (typically 470
nm[6]), they polymerize and harden into the solid filling (for more
information, see Light activated resin)
https://en.wikipedia.org/wiki/Dental_composite#Method_and_clinical_application
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Many materials have so many available energy states that they effectively form a continuum of states. These materials can absorb any wavelength that corresponds to the difference in energy between an occupied state and a higher-energy unoccupied state.
My understanding so far is that when photons are incident upon a body ... the momentum of the photons is ...
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Is it possible to laser cool without using spatially-varying magnetic fields and above zero degrees?
If, for whatever reason, you don't want to use a magnetic field, you can always chirp your laser frequency.
Most ultra-cold atoms experiments starts with a Zeeman slower for a good reason : it's cheap to make and it allows to slow all of the atoms of a given beam with a thermal velocity distribution down to something where usually all of the atoms have a ...
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The Wikipedia article is being a little misleading here. The beam from a laser diverges by an amount which depends on its width not length. The divergence is due to diffraction, and the angular spread of the beam is given approximately by
$$
\Delta \theta = \frac{\lambda}{w}
$$
where $\lambda$ is the wavelength and $w$ the width. But if a laser has a long ...
1
When you solve Maxwell's equations, one of the easiest solutions that can occur is the solution of a plane wave $E e^{i(\vec{k} \vec{x} - \omega t) }$. Plane waves do have a straight forwards interpretation (in homogenous, isotrope media) if it comes to "direction": They "travel" only in one direction.
That is: Their poynting vector ...
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If we assume a Gaussian beam, we have the intensity
$$
I(\rho) = \frac{2P_{tot}}{\pi w^2} e^{-2 \rho^2/w^2}
\Rightarrow
\frac{I(\rho)}{I_0} = \frac{w_0^2}{w^2} e^{-2 \rho^2/w^2}
$$
The knife edge integrates the intensity in one direction, while limiting it in the perpendicular direction. Further note that the exponential has the form of the normal ...
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Two flat regular mirrors do not form a cavity. Diffraction will always cause enough light to escape to make the setup useless.
In order for two flat mirrors to form a cavity they must be of infinite size so that light cannot escape. And the light in the cavity must be a plane wave (zero divergence).
Addendum after edit
Aha. You have one or two ...
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