Light Amplification by Stimulated Emission of Radiation. A means of creating coherent light by either driving an atomic or molecular transition in an optical cavity or firing a beam of electrons through an undulator.

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Validity of Einstein Coefficient Derivations

Consider a two-level energy gap with electronic energy states $E_1$ & $E_2$ and associated population densities $n_1$ and $n_2$ with $E_2>E_1$. In the derivation of the Einstein coefficients ...
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366 views

What's the big deal with Nd:YAG rods?

I see the prices of Nd:YAG rods for lasers, and could someone explain why they are so expensive? Do they need to be mono-crystalline or something? Will Nd:YAG laser work with amorphous/poly-...
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2answers
31 views

How do I find uncertainties in an intensity plot created from a photograph?

I have a photo of a laser beam (taken by sending the laser into a CCD). I then took the image and ran it through an image reader that gave an intensity surface plot. I then took a single cut from that ...
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89 views

Non-semiconductor CW laser types for 445-465nm

Am I missing something in this list of non-semiconductor CW laser types to get emission in the range of 445-465nm? Are there any crystals directly emitting in this range with UV pump? Currently I am ...
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306 views

Does laser beam expand along distance or not? [duplicate]

Why does laser dot become bigger at bigger distance? e.g: from millimeter to inches so that it distracts pilots in aircrafts. I knew that laser beam should't expand over distance, but remain stable. ...
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28 views

Inertial frames and Sagnac interferometers

Let's posit: I am in orbit around a large body, like a planet, and I am close enough to be tidally locked to the large body. Am I in an inertial frame? Even without looking at the stars, couldn't ...
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46 views

What causes this pattern in the reflection of a laser on a screen? [duplicate]

When I shine a red laser behind me at a wall I see a strange reflection occurring on my laptop screen Why does this happen? The pattern on my screen occurs exactly where the laser is hitting the wall. ...
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40 views

Limits on the information obtained through optical measurements

Consider a Gedankenexperiment shown in the figure below. There are two lasers $S1$ and $S2$ with exactly the same specifications on paper. In practice, they are of course somewhat different but ...
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135 views

Carbon fibre laser beam dump material?

A few years ago I came across a material used as a high power laser beam dump. It was made from carbon fibre which looked like a mat made of high density bristles ie all the fibres on the top of the ...
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1answer
71 views

2 level atomic system interacting with Black body radiation. Relaxation time issue

I am studying the transient regime of a 2 level atomic system ($N_1,N_2$) interacting with a blackbody radiation from a source at constant temperature $T_{nr}$. The initial state of the atomic system ...
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119 views

What could cause the gradual loss (or change) of power in a CO2 laser over a long period (e.g. a year)?

For example, if it were a 10W CW CO2 laser that were used for ~45 minutes per day over a period of a year. Would you expect a slight reduction in power with age? Does the dissociation of CO2 occur ...
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101 views

List of laser-cooled atoms and ions [on hold]

I'm familiar with the requirements for an atom or ion to be cool-able with laser cooling -- a closed transition -- or close enough that the leaks can be plugged with repumpers. But is there a list of ...
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138 views

Resonance condition in confocal cavity

In a confocal cavity, a beam traverses the length of the resonator 4 times between two transmissions along the same ray. . For example, in the above figure, path difference between two beams that ...
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68 views

Determine laser cavity modal content from beating / interference?

I'm trying to better understand the modal content and dynamics of laser cavities. I'm specifically interested in mode-locking, although this question is pretty general and applies to CW lasers too. I ...
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0answers
188 views

Laser divergence/convergence over large distance

I have hit a roadblock in my simulation, where there are 2 authors with contradicting equations on the model. So I have simulated both, and drew it out for a few diameters. My dish size is 40m. I am ...
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187 views

Why is Erbium Doped Fiber Amplifier (EDFA) preferred over Erbium Doped Waveguide Amplifier (EDWA)?

Why is Erbium Doped Fiber Amplifier (EDFA) preferred over Erbium Doped Waveguide Amplifier (EDWA)? The question has been asked from an engineering point of view, but obviously I would also be ...
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94 views

Macroscopic chromodynamics

Lately I've been reading about gamma ray lasing phenomena, and I've been wondering about the applications of this. More concretely, the above fantastic question led me to wonder if we could somehow ...
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362 views

Levitation rotation speed involving laser acceleration, pyrolytic graphite and a vacuum

The experment would involve a small NIB magnet levitating between or on the diamagnetic material pyrolytic graphite, unlike other forms of levitation this doesn't require power to run such as ...
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242 views

How is the “negative dispersion” derived?

I'm looking at Kopfermann H., Ladenburg R., Nature, 122, 338-339 (1928) and it appears Ladenburg in Ladenburg R., Z.Physik, 4, 451-468 (1921) was the first to discover the phenomenon of "negative ...
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1answer
148 views

Consistently oscillating micron sized particles in a liquid

I have an idea that would involve the measurement of an oscillating substance whilst the substance is immersed in a liquid. However, the method that I would use to measure the frequency of these ...
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3answers
908 views

Average of $\sin^2 \omega t$, $\cos^2 \omega t$ for long times

I don't understand how the averages mentioned in excerpt below work out. The question is regarding calculating the power spectrum of an oscillating classical dipole. IS averaging over long periods, ...
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3answers
271 views

Can one build a laser using spontaneous emission?

We use stimulated emission and not spontaneous emission to produce lasers. Why is this? Can't we produce lasers by the spontaneous emission method?
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107 views

Laser slow motion

Something really strange happen and I was hoping someone could shine some light on this. I always play around levelers with red lasers. I decided one day to shine a laser through a magnifying glass (...
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2answers
70 views

Is an x-ray maser possible?

I was wondering if lasers evolved from masers. They applied the same principles to a different wavelength. Would it be possible to create a maser at a higher wavelength, using x-rays, gamma rays, etc....
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3answers
706 views

What limits laser pulse duration to single cycle?

Why pulses shorter than single cycle cannot propagate in free space ? Is there fundamental reason or it is engineering ? Is it possible for a laser pulse to have bandwidth that can support half cycle ...
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97 views

Selectively visible laser beam with a controllable means

How can parts of a laser beam be made visible while others left invisible using something electronically controllable (for example, another laser beam crossing it, or a magnetic field, or heat, etc).
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4answers
3k views

How can a laser pointer have range of several kilometers in atmosphere?

Laser pointers manufacturers claim that some pointers have range of several kilometers. Okay, they use a powerful laser, but that powerful laser usually has power less than one watt. Okay, the laser ...
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1answer
53 views

Why does generating EUV frequency combs require femtosecond enhanced cavities?

When generating extreme UV (EUV) frequency combs using high-order harmonic generation, why does the harmonic generation step need to be inside a femtosecond enhanced cavity for the comb to work? More ...
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60 views

Will I see the light?

There is a perfectly smooth wall. We have a slit parallel to it. Through that a laser beam passes. As the slit is parallel to wall the laser beam will hit it normally. So now if I see obliquely I ...
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2answers
31 views

Can you pass 400mJ laser light through a fiber?

What is the energy limit for fibre optics? For a dual-pulsed nd:yag laser firing at 10Hz with energy roughly 2x 400mJ, and pulse width ~5-10ns. My gut says that this is far too high to pass through ...
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124 views

Laser cooling of atoms: more area or more power?

I want to optimise a Magneto-Optical trap. Laser beams come from the the x, y and z directions (positive and negative) and slow the atoms down. Would it be better to increase the beam spot-size (...
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2answers
77 views

How to measure 8 μm surface bumps?

I want to measure surface bumps which are larger in size than $8\ \mathrm{\mu m}$ on a uncoated plastic mirror. So it can be any number of smaller bumps and that would not effect the application. I ...
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4answers
738 views

How to measure the size of a laser dot?

I'm not a physicist, that's why I'm asking you if there is maybe an easy way (e.g. a mathematical law) to measure the size of a laser dot, or its diameter. The setup It contains a laser, a high ...
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3answers
558 views

Calculate the rise in temperature from directed radiation [closed]

For example I have a 1 watt laser and direct it to a sheet of metal (copper), if I were to direct it for say a time interval of 1 minute what would be the change in temperature? I can predict that it ...
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173 views

In what applications are lasers necessary vs. just convenient?

I’m trying to understand, given the wide array of current laser applications: Which applications actually require laser characteristics, as opposed to just use lasers because they are the most ...
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1answer
110 views

Pair production at high laser intensity?

Using high laser intensity to produce electron-positron pair, is it still required interaction with nucleus as is the case when gamma rays are used? What causes the pair creation ?
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2answers
95 views

Ultrafast Lasers

Is the main idea of femtosecond or attosecond lasers is to achieve the high energy or do we have any other parameters achieved by ultra-fast lasers ?
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1answer
241 views

Can the inverse of a laser exist?

Speaking as a layman, I understand a laser works by exciting an electron so it returns to rest by emitting a photon. Is it feasible to 'damp' the energy level/s of an electron so it absorbs energy ...
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34 views

What is the difference between ultrafast laser and normal laser?

I was reading an article of latest innovation and i came across this 'ultrafast laser' term. What is the difference between it and the laser we normally refer?
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1answer
77 views

Effect of the refractive index of a transparent layer coating a particle?

I am modelling a cell as a particle coated by a layer of a material whose refraction index might change. This layer is to resemble the membrane. The purpose of the model is to simulate what happens ...
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1answer
77 views

What could cause a diode laser to be emitting the half-harmonic of the fundamental frequency?

I have a 405nm laser which is seemingly outputting a small portion of 810nm light. I am wondering what mechanism this could be caused by. Is this a down-conversion phenomenon or perhaps just another ...
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1answer
450 views

What is a lineshape function $g(\omega_0)$ in a Laser?

I am a newbie to the world of lasers and was working my way through some basic problems, when I encountered this one: Optical Electronics, A.K. Ghatak and K. Thyagarajan (Cambridge University ...
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1answer
111 views

Is lasering some natural phenomenon soemwhere?

Laser is actually the simplest kind of light, from a physical point of view. Many people think it is some rocket science simply because it is not natural but takes some human efforts to create. So, ...
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2answers
184 views

How can the thrust due to radiation pressure be amplified in photonic laser thruster?

The thrust is amplified due to repeated bouncing of photons between two mirrors as shown in the diagram in this: Why does repeated bouncing of photons produce amplified thrust when the answer in '...
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1answer
3k views

Heating metal with laser? [closed]

Can a laser be used to heat metal's to the point they glow red? How are laser cutters able to cut metal very easily? How much heat can a laser generate?
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1answer
91 views

How can net output of photons in laser occur?

The way I see it, in both spontaneous and stimulated emission, one atom being de-excited would result in one photon being produced. So if we excite $10^{23}$ atoms, only $10^{23}$ photons would be ...
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1answer
231 views

Ideal four-level Gain Medium (or just any old gain medium)

What exactly is happening in a laser's gain cell when the irradiance is greater than the saturation irradiance? Also can someone offer a clear conceptual treatment of the gain-coefficient and its ...
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1answer
258 views

Does Combining Lasers Add to Their Power?

For example... If I had a 2W green laser, a 2W red laser, and a 2W blue laser, could I combine them using crystals to form a 6W white laser? Or is that now how it works? If not what would be the ...
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33 views

Projects to undertake Using Lasers [closed]

I need an economically feasible physics project that would use lasers in any manner preferably with respect to optics for a school projects class XII . Any suggestions are welcome no matter how crazy ...
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1answer
101 views

Does this length refer to wavelength or length? [closed]

In this question: A He-Ne laser emits red light of the wave length $\lambda = 632.8\ \mathrm{nm}$ with a beam diameter of $2.0\ \mathrm{mm}$ and a power output of $1.0\ \mathrm{mW}$ [...] (d) How ...