# Tag Info

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If I wanted to laser cut combustible materials, I would do so in an inert atmosphere - no oxygen, no burning. Of course you can never prevent local charring - chemical decomposition due to heat - but you can prevent a chemical reaction with oxygen by removing the oxygen. Other than that, careful control of the laser intensity and time profile can help: a ...

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You are making an incorrect assumption in your question: There is no physical evolution from a number state (aka Fock state). This evolution happened purely inside physicists' heads as it was realized that laser light is not properly described by number states. The problem is your assumption that the particle number ever is well-defined. Lasing action is an ...

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The wire is a cylindrical reflector. The laser light that hits the top of the wire is reflected upwards; the light that hits the side is reflected sideways. This is simple reflection - no need for a diffraction explanation.

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Light has properties of waves and particles and doesn't necessarily travel in "straight lines". There is an interesting experiment (I will look up the original scientists who did it and post that info here) where they set up basically a cardboard circle in front of a wall and then shine a flashlight at it. Interestingly enough, there is a shadow in the ...

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The answer to your question is no. Mixing a purplish (405 nm) and green (532 nm) laser does not produce a bluish beam at 468.5 nm. If you were to shine both lasers into your eye (which you should never do), the resultant effect would look bluish though due to the physiology of the human eye. However, it is possible to mix two wavelengths of light to ...

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Note You should never, ever look at a laser. It can cause irreversible damage to your eyes, including blindness. Now for your answer. Yes-ish It will appear to be something in between, as you can see from a color wheel. However, you should note that this would be the color you see if you reflected the beam off of something. It should be noted, however, ...

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The efficiency of the pumping source is $x$ means that $x$ amount of electrical power is converted to energy which is useful for pumping the laser medium. The absorption of the pump is $y$ means that $y$ amount of the energy from the pump source is actually pumped into the medium to generate the population inversion necessary for lasing. The total amount ...

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Searching that book for "lineshape function" will return this page, which explains what that means. Essentially, the atoms in the gain medium are usually able to respond to frequencies $\omega$ which are close to, but not necessarily exactly equal to, the central frequency $\omega_0$. The response is strongest at $\omega_0$ and then it tapers off over some ...

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The only natural lasers I know of are astrophysical. For example a natural infrared laser in the vicinity of the star MWC 349 was discovered in 1995. If MASERs count then a number of them are known. There's a review in this paper.

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There are some other options I can add. By using two cylindrical lens you can build a beam expander that only expands in one direction, thus correcting for the elongation of the beam. Once you have corrected for this you can then focus the beam on to a pinhole spatial filter. This would only partially work since the laser needs to have a Gaussian profile ...

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One of the pitfalls of trying to answer "what would this look like" types of questions is that, in quantum processes, the act of "looking" often necessarily changes the picture. The problem with your specific question is that it seems to presuppose that the electron is "actually" a small, fast-moving object that if we could only have a quick enough shutter ...

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I don't agree with the comment of Chris Mueller - the same rule applies to other pumping methods as well. We cannot reach population inversion for states $|1\rangle$ and $|3\rangle$ no matter how we pump, but if lasing would happen from $|3\rangle$ to $|2\rangle$ and state $|2\rangle$ would quickly relax to $|1\rangle$ then we could get population inversion ...

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Here are some of the relevant bits of physics/questions to ask: To cut a material, it needs to absorb heat faster than it can lose it. heat is conducted away: this is typically linear with temperature gradient heat can be radiated away: this is more important at higher temperatures (follows $T^4$ relationship) laser power may be reflected or absorbed: the ...

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The Poynting vector $\vec{N}$ is the power per unit area of your beam. If the beam is perfectly absorbed, then the force is given by $$F = \frac{1}{c} \int \vec{N} \cdot d\vec{A}$$ So, providing you have the beam incident normally upon something, the force on it will just be the power of the laser divided by the speed of light. Of course, if the light is ...

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Heat is random motion of atoms. In doppler cooling, lasers are slightly below a transition frequency when viewed in the lab frame of reference. Atoms moving faster than average toward the beam see it blue shifted just enough to absorb a photon. These atoms all receive a kick that reduces their kinetic energy. Now they are excited. They decay by emitting ...

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In principle, yes, but for clear air the scattering is very very weak, and the scattered light would probably be drowned out by other background sources, especially the blue sky. It would be easier at night. If the air is not clear, but instead is carrying dust or water droplets or smoke, the beam would be easily visible and recordable, again much more ...

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Yes The image below shows the Keck telescope's laser guide star. It is designed to excite sodium atoms in the mesosphere. These excited sodium atoms flouresce and act as an artificial star which allows the telescope to correct for optical aberrations caused by Earth's atmosphere.

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Lets start with some assumptions. You probably have the beam from a laser pointer in mind so the hole size you want to burn is about $4\,\text{mm}$ in diameter. Lets assume that it's roughly $-5^\circ\text{C}$ ($23^\circ\text{F}$) outside. One final assumption, and this one is just a guesstimate, lets assume that due to thermal conductivity you need to ...

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It depends on the photon energy. Stimulated emission happens when the photon energy matches the energy difference between the metastable and ground state. Excitation happens if the photon energy matches the energy difference between the metastable and some excited state. If you found a system where the metastable to ground and metastable to excited state ...

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Let's look at the primary constituent of air, nitrogen. The ionization energy of nitrogen is approximately $1400~\text{kJ/mol}$. This works out to be approximately $2.25\times10^{-18}~\text{J/atom}$. The energy content of a laser beam is $E = h c /\lambda$. This means we can solve for a wavelength, $\lambda$ that provides enough energy to ionize a single ...

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High quality, monochromatic laser beams are governed by diffraction instead of geometrical optics. Talking about rays doesn't really tell the full story. The parameter of a laser beam which expresses how well collimated it is is called the Rayleigh range, $z_R$. The units of $z_R$ are units of distance, and you can think of it roughly as 'the beam will ...

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I'll leave the practicalities to the two other great answers (Floris's and boyfarrell's because I want to focus on one of your statements: "...focusing and collimating ...which I guess are contradictory objectives, or are they?" Absolutely not. In a weird kind of way they are the same thing: or kind of dual concepts. They are if you like two extreme ...

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For a laser beam to be narrow and stay narrow, you need parallel beams. The usual approach is to focus the beam onto a very small pinhole (say 10-20 µm or so), then focus a second lens on the pinhole (expander). The fact that all rays have to pass through the very small point means that any diverging components of the beam will be intercepted by the pinhole; ...

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Astigmatic correction to improve the shape Diode beams are usually rectangular when collimated because the have a fast and slow axis. You can expand the slow axis such that the beam shape is much more rectangular. An easy way to do this is to make a beam expander with a pair of cylindrical lens. A beam expander to increase the diameter when collimated ...

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