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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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 ...
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20 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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47 views

Stimulated emission in LASER

I have been reading about how lasers function : A photon is used for stimulated emission of electrons from the metastable state to a lower energy state. What I don't understand is : How can "giving" ...
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41 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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32 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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50 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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50 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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56 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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54 views

Would a giant satellite laser work as a weapon?

If someone built a satellite to float about in space, which used mirrors to focus and magnify energy from the sun directly into one direct spot (like in the James Bond film Die Another Day) would it ...
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59 views

List of laser-cooled atoms and ions

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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86 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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57 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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148 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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149 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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93 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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318 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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229 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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389 views

Maxwell's Demon - laser cooling

There’s an interesting article on Scientific American that tells how to cool individual atoms to within a very tiny fraction of Absolute Zero. It uses two laser beams acting on a very cold rarified ...
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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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10answers
865 views

How far can light go?

When a ray of light is projected, (say) from the surface of Earth to outside in space. The condition is that, there is no obstruction to it till infinity (it travels only in vaccum). My question is ...
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3answers
155 views

Is the output of a laser pointer polarized or not?

How to verify it? Is a laser necessarily polarized? I have a laser pointer with wavelength 532nm in hand.
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3answers
642 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
220 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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3k views

From power of a laser beam to electric field amplitude

In my experiment, I use a laser beam with wavelength $\lambda=894 \text{nm}$ for some magnetic resonance experiment. Right now, I'm doing some calculation using Quantum Mechanics, which requires the ...
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2answers
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How would a laser gun actually work?

So, let's assume that the "laser gun / phaser / beam weapon" from all sorts of Sci Fi were an actual thing. You know - a weapon that uses a laser to kill somebody. I'm trying to imagine the physics ...
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3answers
378 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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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
2k 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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4answers
323 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
225 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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3answers
155 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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2answers
86 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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30 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
54 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
154 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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88 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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2k 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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62 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
160 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
45 views

Spectral Line- Width

How does the spectral line-width of light source (let that be ordinary light, LED, LASER etc.) decides for which communication purpose it will be used for ? Is it like spectral line-width effects the ...
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1answer
95 views

Why do we see brown light?

While researching about lasers (it's my hobby), it suddenly hit me: there are lasers for every color of the visible spectrum, but there are no brown lasers. Brown isn't even on the rainbow. How is it ...
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1answer
23 views

Optical pumping without stimulated emission

If I want to pump Rubidium 87 atoms From fg = 2 to fe=1 level with a laser tuned to D1 transition and avoid stimulated emission then it is sufficient that I use a laser power which gives me an ...
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1answer
35 views

Gaussian beam shape

In this diagram of a Gaussian beam, why does the radius vary with z position? Is it assumed that a Gaussian beam is always being focus by a lense? Why can the beam not go any smaller than $w_0$ and ...
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1answer
67 views

does photon travels in a helical path in an optical vortex?

The wave front of the optical vortex beam is helical. Does it mean that the photon travels in a helical path? When the optical vortex beam is focused on a screen, an annular ring with dark center is ...
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2answers
67 views

Why lasers and not light? [closed]

Some laser applications consist simply concentrating light into a small spot (e.g., image projection, welding, cutting, etc.). Why are lasers used instead of a simpler light source?
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2answers
99 views

What wavelengths to combine to get 488nm?

Is it possible to combine a blue and green lasers to get cyan? If I used 405nm and 532nm, would I get (405+532)/2= 468.5nm? Is this a correct calculation?
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2answers
154 views

Convert normal white light to laser-like light?

Is there a probable device that can convert white light to laser-like light without the need of an electrical stage in-between? I'm thinking of something along this level. A very precise filter and ...
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2answers
107 views

Why does light from a laser end up in a concentrated spot?

I've heard from several people that photons will always take the past of least action while travelling, so why does laser light projected on a surface appear concentrated to a single spot when ...
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1answer
106 views

What would a laser beam's E-M waves actually look like if you zoomed in?

I am trying to understand how a real world beam of laser actually reflects the physics description of oscillating electromagnetic waves. So say we are looking side on at a vertically polarized laser ...
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3answers
128 views

Can stimulated emitted photons be absorbed?

Typically a stimulated photon will be one of a pair with its stimulating photon. If the leading photon is absorbed by a particle in the ground state, will it then be re-emited by the stimulated ...