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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3k views

Is the “How to break the speed of light” minute physics video wrong?

I am referring to this video, on YouTube, by minutephysics, which has quite a lot of views. In the video it states that if you flick your wrist while pointing a laser that reaches the moon, that the ...
4
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4answers
248 views

Why do lasers require mirror at the ends?

Laser uses mirrors to reflect photons in order to stimulate atoms to emit photons, but why this is so?. I mean, why does a photon stimulate atoms to produce more photons? If a photon made an atom to ...
18
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4answers
1k views

Is it possible to observe interference from 2 independent optical lasers?

It seems that if the coherence length of a laser is big enough, it is possible to observe a (moving) interference picture by combining them. Is it true? How fast should photo-detectors be for ...
11
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4answers
515 views

When lasers are used to cool atoms or ions, etc where does the heat go?

According to the first law of thermodynamics, sourced from wikipedia "In any process in an isolated system, the total energy remains the same." So when lasers are used for cooling in traps, similar ...
5
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3answers
679 views

Recently publicized experiment on destructive interference between two laser beams

Recently I've had several non-physicist friends ask me, independently of each other, about an experiment where two collinear laser beams destructively interfere along a certain length. Everybody wants ...
7
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6answers
2k views

Why does a laser beam diverge?

I was wondering why a laser beam diverges. If all the photons are in the same direction, I would imagine that it would stay that way over a long distance. I am aware that a perfectly collimated beam ...
4
votes
2answers
346 views

Rocket propelled by a giant monochromatic laser

I am preparing for my quals and stumbled across the following problem, and although it only requires undergraduate-level physics, I feel I can't piece everything together. "A rocket of mass $m_0$ is ...
2
votes
4answers
9k views

Free Optics Simulation Programs

I'm having an extremely difficult time finding an optics program that is easy to use and offers accurate physics simulations. I'm not asking for much, I just want to be able to simulate a laser going ...
1
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2answers
1k views

Can energy be extracted from clouds?

Can cloud charge imbalance be used as an energy source? First off quite some energy must be present in clouds: a lightning path is quite long, and electrical breakdown of air requires about 1MV/m. ...
3
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1answer
135 views

What determines the form of the intensity curves in Laser-Induced Fluorescence (LIF) measurements?

What determines the form of the intensity spectra of different particle species in Laser-Induced Fluorescence (LIF) measurements? See e.g. I figure that bigger particles have more ways to get ...
3
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2answers
875 views

Propagation of light in transparent media: absorption and reemission or scattering?

In the two Phys.SE questions What is the mechanism behind the slowdown of light/photons in a transparent medium? and Why glass is transparent? transparent media were discussed. But I'd like to clarify ...
12
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2answers
1k views

What is an intuitive explanation of Gouy phase?

In laser resonators, higher order modes (i.e. TEM01, etc) accumulate phase faster than the fundamental TEM00 mode. This extra phase is called Gouy phase. What is an intuitive explanation of this ...
14
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2answers
598 views

Why doesn't the no-cloning theorem make lasers impossible?

As I understand lasers, you start off with a few photons that are in an identical state, and other photons that are created later tend to have the same quantum numbers due to Einstein-Bose statistics. ...
13
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6answers
3k views

Tried to do the double slit experiment, failed. Why?

I tried, and failed, to do the double-slit experiment. I thought I had a good experiment setup, but obviously I was wrong. Can anyone offer some insight in what I might have done wrong? Most of ...
12
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1answer
699 views

Is the time reversed laser really a laser?

I'm looking at the time reversed laser and I was having trouble understanding why we call this device a laser. To me this device is more like the absorbers found in FDTD codes, something like a CPML. ...
8
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3answers
513 views

Why use lasers for intense, localized heat instead of some other light source?

Lasers are used in various industrial processes that need intense, localised, heat (3d printers and laser cutters come to mind). My question is: why use lasers? There are many other (cheaper, ...
8
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3answers
1k views

Can radio waves be formed into a pencil beam?

Laser beams are said to have high "spacial coherence". This means that the beam is highly concentrated even at long distances (low spread). Can this be achieved with radio waves (much longer waves) ...
4
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1answer
490 views

Focusing laser & off-axis illumination & diffraction limit

I've thought I had a good understanding how resolution enhancement tricks works for projection lithography, until I tried to understand if it's possible to get sub-diffraction performance for focused ...
2
votes
3answers
284 views

Lasers and Collimation

If lasers are collimated, what causes them to decollimate? Their production system seems to suggest a completely linear, collimated light source, but they do spread out over large distances. The same ...
11
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4answers
209 views

Does the speed of medium affect the path of light?

Let's say I shine a laser from a stationary medium into a moving medium (suppose the water is moving very quickly) perpendicular to the interface and back to a stationary medium like this: (Note: ...
7
votes
2answers
505 views

How does infrared light 'erase' phosphorescence on zinc sulfide?

I found some sheets of zinc sulfide in my basement that phosphoresce green for up to 24 hours or so after exposure to bright light in the violet range or shorter. One of the first things I tried was ...
4
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2answers
365 views

Optical Drive Physics

I have been recently wondering how is data stored on and retrieved from optical devices like CDs, DVDs, and Bluray. What makes these different storage types different from each other?
8
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1answer
1k views

Why do we see laser beams?

A laser produces a coherent beam of photons with particular $\mathbf{k}$ and $\mathbf{\omega}$. So, if there is no particular $\mathbf{k}_0$ directed toward our eyes, why do we see laser beams? I ...
7
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2answers
346 views

Fairly Broad Spectrum Light Source Options

I tried this sight before to find filtering options and got fantastic results, so let's try again! I am setting up an experiment that requires light of two different frequencies (445nm and 350nm). ...
6
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2answers
398 views

Good introductory papers and books on laser physics and pulsed lasers

I am looking for good introductory papers and/or books on the principles of lasers. In particular, I am interested in pulsed laser technology. I understand that Gould, R. Gordon (1959). "The ...
4
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2answers
95 views

Can we fire a single femtosecond pulse of light without an associated train of additional pulses? What sort of equipment allows for this?

What sort of mode-locked laser systems allow for the production of single isolated pulse of light (as opposed to a train of more than one pulse), where the individual pulse duration is on order ...
4
votes
3answers
290 views

Counterpropagating beams in a ring cavity lasers

Ring cavity lasers usually has a intracavity element like a optical diode to forbid standing wave pattern and, consequently, spacial hole burning and related instabilities. So, my question is: why to ...
3
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1answer
80 views

Polarization in Lasers and Liquid Crystal Displays

When we talk about Polarization in Lasers we mean placement of the crystal at Brewster angle to block the s-polarization and only the p-polarization will survive. How do we compare the term ...
3
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1answer
362 views

gamma ray lasers?

Is it really possible in the foreseeable future to create a gamma ray laser? I've read these two articles on Wikipedia: the Hafnium controversy Induced gamma emission It sounds pretty amazing, ...
2
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1answer
238 views

What is 'tilt locking' of a laser cavity?

In another question, jasonh mentions a scheme for locking a laser to a resonant cavity called 'tilt locking': The signal is used for locking the frequency of a laser to a high finesse cavity. The ...
1
vote
3answers
71 views

Young double slit experiment without first slit

What if I take a laser pen and direct it towards the middle of two wide slits? Will I get interference pattern or just two lines? Do I need to scatter photons before they hit the slits to observe ...
0
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0answers
63 views

Lasers can demagnetize ferromagnets?

How is it possible to demagnetize a magnet with a laser? Source: http://www.helmholtz-berlin.de/pubbin/news_seite?nid=13657&sprache=en&typoid And the paper: ...
0
votes
1answer
94 views

Why does mode hopping occur through a change of temperature?

Why does mode hopping occur when the temperature of a diode is changed? Why is a similar effect seen when we change the electric current?