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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262 views

Accurate way to measure angular spread of a laser beam

While doing an experiment to measure the angular spread (or say divergence) of a beam of laser (which in my case was an inexpensive diode laser), what is the most accurate way of measuring the ...
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1answer
31 views

Proton 'Laser' ? could we get a laser-like effect? [closed]

This is a speculative question. question: Can we gain protons, by smashing a high speed proton into a hydrogen plasma? Background: I was thinking about how lasers repeatedly send the photons thru ...
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2answers
80 views

Can one stimulate emission of a photon with an energy different from the emitted photon?

Suppose I have a three-level system with $E_0$ the ground level, $E_1$ the intermediate and $E_2$ the upper level. In thermal equilibrium they will have a certain probability distribution according to ...
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1answer
46 views

Estimating quantum efficiency of gated avalanche photodiode

I have a photon counting system that uses a gated avalanche diode to detect single photons. The repetition frequency of the gates is $f_1$ and the temporal gate width is $\tau_1$ (so the duty cycle is ...
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1answer
99 views

What does (simple) $j/cm^2$ represent AND how does this result $6.959j/cm^2$? [closed]

According to the image shown below, this specific Laser Hair Treatment device claims that it has a concentration of $6.959 j/cm^2$. So far by research I have found that it needs around $6\mbox{ to }7 ...
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2answers
246 views

How to be sure that a He-Ne laser light is monochromatic

How can I be sure that the emission of a He-Ne laser contains only one single mode of laser cavity? The only thing that I know is that if I use a diffraction grating and the light isn't ...
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1answer
158 views

Help with the Heisenberg relation in Gaussian wave

In short laserpulses there is a minimal product of the frequency width and the pulselength for Gaussian pulses $\tau \cdot \Delta\omega \geq4\ln2$ this is the fourier boundary. So I know it origins ...
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1answer
115 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?
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1answer
251 views

Laser action on one side mirrors (half silvered) and prisms

I know that half silvered mirrors are used in the production of laser emission. Can half silvered mirrors be used outside the instrument so the rays get reflected back on one side of the mirror and ...
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1answer
75 views

I want some information about population inversion in graphene & build laser with this theory

I have read the paper Theoretical Study of Population Inversion in Graphene under Pulse Excitation. A. Satou, T. Otsuji and V. Ryzhii. Jpn. J. Appl. Phys. 50 no. 7, pp. 070116-070116-4 (2011). ...
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2answers
558 views

New infrared laser weapon made by the USA - How does it work? [closed]

I have seen this post: New infrared laser weapon, the Laser Weapons System, could shoot down drones or disable ships: US Navy You can watch the video as well. that exhibits a laser weapon which can ...
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1answer
6k views

laser spectral width vs. linewidth

I have been racking my brains over the differences between laser spectral width and something called the linewidth. The linewidth was written about in detail by Henry in 1982. The spectral width is ...
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0answers
11 views

Doppler and recoil limit on temperature

I havent't understood the causes of Doppler limit and recoil limit. I have found on the net different observations about them ("Doppler limit is due to the fact that the atom can't have a smaller ...
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0answers
17 views

Why does a circle of light form around a wire when a laser is pointed at it? [duplicate]

Referencing this video: https://www.youtube.com/watch?v=9Q_4SNbpBfo Why does a circle of light form? I've seen previous Phys.SE posts on this topic relating the answer to reflection, but I have ...
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0answers
7 views

What is meant by the (aperture size) of optical deflectors in laser scanners?

How do you measure the aperture size in a laser scanner.
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2answers
34 views

Calculate required power output for a laser

How to calculate power rating required for a laser in order to produce a dot at a specific distance after reflection? For example, the laser is 10cm from the mirror, at an angel of 30 degrees it ...
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0answers
36 views

Would an inverted design of a laser phosphor display (LPD) work?

Background info... It is my understanding that a laser phosphor display works by emitting RGB laser beams through a mechanism that cycles them in a pattern similar to a cathode ray tube. When I read ...
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0answers
22 views

Losses in a laser diode

How do I convert loss/gain from units of /cm to /s? Intuitively, I would say multiply loss in /cm with the group velocity c/n, where n is the refractive index. Am I missing anything?
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0answers
39 views

Entangled Photon (laser pointer)

From a laser pointer emission; is it creating entangled pairs of photon? is it possible to get more than "pair" entangled, like group of photons all entangled?
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0answers
45 views

Photons and gravity [duplicate]

A very powerful laser pointing to the empty space next to small object in space. The photons in the laser beam does not hit the object. Will the small object be gravitationally affected by that laser ...
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2answers
27 views

Laser beam sensed by scattering

Can a laser beam, whether it is a IR laser or of the visible to human eye spectrum, be seen/sensed by an electronic eye like a photosensor/photodetector, not human eye, if the beam is just in air? For ...
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1answer
34 views

why is it that the photon incident on metastable state stimulates atom to go into ground state but not to even higher energy state?

isnt it possible that photon incident on atoms at metastable state goes to further high energy state rather than the ground state? whilist there is always that stimulated emisson taking place. why ?
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28 views

Why does Threshold current of laser increase with the increase in temperature?

Why does Threshold current of laser increase with the increase in temperature? I know that at the same current level, the power is higher at lower temperature but why?
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0answers
69 views

Photoelectric-effect laser

The question is whether it is physically possible to build a laser using only the photoelectric effect in the vacuum, with no lasing material. I know that there is a whole history of laser ...
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0answers
38 views

What is the best laser wavelength to melt a certain material to the point of 'welding' together

Assume the material is enough of a heat sink that you can hold the torch to the material and the spread of the red-hot metal is not moving - is stabilized, but you can still melt the material in the ...
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1answer
55 views

How does airborne laser system deflect the laser beam?

In the Airborne Laser system, the laser beam is directed from the nose of a Boeing airplane towards the target. In this system, the angle of laser beam with respect to airplane body can be changed at ...
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0answers
92 views

Lasers without Population inversion?

When I made a study on lasers, I found a webpage saying that the quantum mechanical principles enable us to create laser action without population inversion, which Einstein suggested as one of the ...
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0answers
38 views

When optically pumping a lasing gain medium with another laser, does Stimulated, or Spontaneous emission dominate?

Much of my reading seems to indicate that laser pumping results in a fluorescent stokes shift but somehow photon vector is maintained. I've seen the phrase "Spontaneous Fluorescence by Stimulated ...
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0answers
41 views

Can multiple lasers be concentrated in a circular area using some optical arrangements?

Can multiple lasers be concentrated in a circular area using some optical arrangements such as using a paraboloid surface? If yes, why do in high laser power systems do they use only 2D arrays of ...
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0answers
26 views

Calculate rotational duration of magnetic levitation inside a vacuum chamber?

Background Numerous examples show rotating pyrolytic graphite (or similar diamagnetic material) that can be moved using a laser. Problem The problem has the following objects: An N52 grade ...
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0answers
19 views

What is meant by spatially multimode states of light?

I came across this term while reading texts on Quantum Optics and Lasers. While I know something about multimode laser oscillations, I am unsure about what is exactly meant by multimode light?
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0answers
24 views

Are there examples of “loss-less” Forster Resonance Energy Transfer (FRET)?

When I think of a Forster Resonance Energy Transfer (FRET) process, I typically imagine the initial excitation of an absorbing chromophore with a photon followed by the subsequent emission of a lower ...
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0answers
76 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: ...
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0answers
138 views

Determing aperture size for space-based-solar-power laser transmitter

I have hit a bit of a roadblock in my simulation. In the equation I require the aperture size for the laser source. $$I_a ≈ \frac{\lambda d}{A}$$ $I_a$ = aperture atop the atmosphere ($m$) ...
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0answers
50 views

What highest amount of energy can we get from a laser?

Can we get high energy from laser like fusion and fission reactions ? what is highest energy we can get from laser ?
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0answers
41 views

Welding physics (black body and heat conductance)?

If I have two pieces of steel that I would like to weld with a laser (say $d$ in diameter). If I wanted to melt the two pieces to a depth of $d$ along the edge and then combine them together, how much ...
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0answers
58 views

Time reversed laser

Recently, I read an article on time reversed laser. I don't know why they call it a time reversed. I have a doubt that why they use two laser in the device. And what is an anti-laser? The device ...
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1answer
828 views

Increase of threshold current by temperature in a laser diode

I read somewhere that if we increase the temperature of the material in a laser diode the threshold current for lasing also increases. Can someone explain to me why is this happening? What is the ...
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2answers
236 views

Can a detuned laser can excite an atom? How?

Can a detuned laser can excite an atom? If so, how is this possible?
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1answer
103 views

Density and statistical models for visible air dust

If a laser beam is looked at from the side versus a dark background, a sparkling effect can be seen caused by dust particles in the air hit by the beam. Is there any simple model or coarse ...
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1answer
388 views

How does a Blu-Ray work? [closed]

I've just bought a BluRay, and I want to know how it works. I'm not searching for a high-level scientific explanation--just a simple answer.
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0answers
14 views

Plasma wakefield acceleration for Protons

Laser plasma acceleration is a promising technology that could replace the current method of accelerating particles (which is via electric fields). It is somewhat cheaper also as it makes the ...
-1
votes
1answer
45 views

Does it take a lot of energy to heat metals up?

Why does it take a lot of energy to heat metals? And to do it quicker it requires much more energy? What about the use of lasers would that be an efficient process that is quicker and requires less?
-1
votes
1answer
93 views

How does laser induced fluorescence in excited atoms work?

Atomic clocks use laser induced fluorescence in order to detect excited atoms, how does this work? Apparently the clocks need to detect the states of nearly 100% of the atoms being examined. In an ...
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votes
1answer
55 views

Why is it necessary to supply constant electricity to make a laser work?

As we know that in lasers there are excited atoms. When energy is provided in the form of light, heat or electricity to these atoms, these excited atoms after sometime go to a lower state of energy ...
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3answers
312 views

A Different Lasing Medium [closed]

Powerful lasers are highly intense, diverge negligibly and are also coherent. These radiations are emitted through partially reflecting mirrors after simultaneous reflections within the lasing medium. ...