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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88 views

Options to correct rectangular laser beam profile?

We recently switched to a 405 nm laser diode which has a terrible beam profile -- it is a well-defined rectangle with an aspect ratio of about 10:1. The image below shows the collimated beam which ...
2
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1answer
65 views

Propulsion force on a laser pointer?

How to calculate propulsion force on a laser pointer in reaction to the emitted light power in watts? Should I just divide power by speed of light? Since power is energy per unit of time, hence ...
3
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1answer
60 views

Can you thermally pump a laser? (and problems with population inversion)

Recently a question was asked during a lecture about the possibility of thermally pumping a laser. The lecturer claimed that this is pretty impractical as typical transitions in the visible light ...
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1answer
42 views

Using attosecond laser pulses to view electrons

It is often said in popular media sources that creating shorter and shorter laser pulses will allow us to view electron dynamics as they happen in chemical reactions. This is obviously beneficial in ...
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1answer
44 views

doppler cooling temperature limit

Wikipedia shows a heating effect that causes minimum temperature achievable in doppler cooling as: "The atom performs a random walk in momentum space with steps equal to the photon momentum due to ...
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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 ...
3
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1answer
75 views

How powerful would a laser need to be to make a hole in snow?

How strong would a laser beam have to be (and what frequency would be optimal) for it to be able to make a hole in snow? Here I am looking for a laser beam that could make the hole after less than 2 ...
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1answer
33 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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1answer
382 views

Can a UV LED cause air ionization?

I am thinking of the high power LEDs at around 250nm wavelength and an output power of some 30mW optical, in continuous mode either divergent beam or focused.
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4answers
155 views

Focusing and collimating laser light on a table top scale

I am looking for a summary of practical methods of focusing and collimating laser light, which I guess are contradictory objectives, or are they? For example, when I use typical small diode lasers, ...
2
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3answers
71 views

Laser beam photon counting

I'd like to know if devices exist that are able to detect the single photon missing out of a normal laser beam. I am aware of the fact that single photon counters do exist, but I'd like to ask some ...
2
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1answer
54 views

Short Laser pulse in near field bandwidth

Is there a way to create a short laser pulse that has, at least in the near field, a very narrow frequency range?
7
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2answers
450 views

How do I find the right lens for my laser?

I purchased this line laser recently and I'm running into a bit of an issue. The laser shoots out at a 120 degree angle which is perfect. However, once the laser spreads to about 4.25 inches, I need ...
5
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1answer
635 views

Laser, wire, and a circle of light

So, when I point a laser at a piece of wire (pointed at a specific angle), a circle of light appears on a wall behind it (see image below). I am trying to see why this happens and if there are any ...
0
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1answer
164 views

Particle-in-cell (PIC) code Virtual Laser Plasma Lab (VLPL)

I am writing a simulation code to model betatron X rays produced by electrons accelerated using laser wakefield acceleration (LWFA). I have heard about 3D PIC (Particle-in-Cell) code VLPL (Virtual ...
2
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0answers
40 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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4answers
165 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 ...
0
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1answer
47 views

How to determine the strength of a laser beam needed to cut through a specific material?

How can it be determined how strong a laser beam needs to be in order to cut through specific material? For example, if I have a 5mm thick piece of brown cardboard, is there a way to determine how ...
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0answers
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?
2
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1answer
270 views

Can very high power laser beams self focus in vacuum?

I first recall reading about such an effect in a SF story entitled "Rails Across the Galaxy" which involved self focusing laser beams. And in a science paper here
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2answers
98 views

Laser power consumption vs power output

I have a 5 mW laser pen powered by a 1000 mAh 3.7 volt battery that takes over 2 hours to recharge. It drains it in 15 minutes. Why is it only called 5 milliwatts output if it is consuming 14.8 W?
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0answers
68 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 ...
2
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2answers
120 views

Does a laser beam have to hit the eyes in order to damage them?

Does a laser beam have to hit the eyes in order to damage them? Or can a persons eyes get damaged by looking at a beam that goes past their eyes (e.g. looking at a laser beam moving inside an ...
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1answer
38 views

How to choose laser goggles for low-power laser of specific wavelength

I need to choose laser goggles to shield eyes against 678 (+/-8) nanometer laser (5mW power). The laser has a red beam. I found for example some goggles that are sold for 650nm, with a blue lens. ...
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2answers
95 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 ...
3
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2answers
228 views

How we see laser light if it travels in a straight path? [duplicate]

Light travels in straight path, and our eyes detects an object's reflected light then we see the object. So if laser light is going in a straight path, how come we can see laser light?
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2answers
92 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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2answers
73 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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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
115 views

Minimum spread of frequency and wavelength in neodymium laser

What is the equation linking the minimum spread in wavelength and frequency of a pulsed laser, in relation to the lasers pulse time and operational wavelength. For example: If a Neodymium laser ...
2
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1answer
47 views

How to propagate a (tilted) gaussian beam through a telecentric f-theta-lens

My questions has two parts: First of all let's assume I have a gaussian beam and I send it through a telecentric f-$\theta$-lens (e.g. http://specialoptics.com/products/scanning_confocal.html) with ...
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3answers
157 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 ...
3
votes
1answer
111 views

Phase noise and linewidth of laser

I learned that the linewidth of a single frequency laser is closely related to the phase noise. But this sentence from a book completely confuses me: "A quantum-limited beam in a so-called coherent ...
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2answers
42 views

Practical Uses of Laser Attenuation

In my college physics lab, I am studying the attenuation of a laser through different concentrations of copper sulfate. I am curious about the practical uses of laser attenuation. Why do we study it? ...
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10answers
554 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 ...
0
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2answers
97 views

Gaussian beam modelling, location of the beam waist?

In reference to the specifications of a laser diode below: http://www.thorlabs.de/thorcat/11900/L780P010-SpecSheet.pdf I wish to be able to model it as a gaussian laser beam. I understand there is a ...
23
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5answers
2k views

Quantum random numbers from a laser — simplest setup?

I'm a software / maths guy who would like to build a physical setup for generating quantum random numbers. I have no physics background, so bear with me. Background The project is for a public ...
6
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2answers
151 views

How is the phase of the stimulated emission in a laser first “chosen”?

As I understand, once you have a population inversion and the excited atoms decay they will emit in random directions, and the ones that emit along the axis of the medium will cause stimulated ...
2
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1answer
73 views

Why are laser pulses Sech Squared in temporal shape?

Ultrashort pulses from mode-locked lasers often have a temporal shape which can be described with a squared hyperbolic secant ($\mathrm{sech}^2$) function: $$ P(t)=P_0 \mathrm{sech}^2 \left( ...
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3answers
3k views

Is it possible to make laser beams visible midair without smoke?

My question is: Is it possible to make laser beams viable midair without smoke? I thought it would be a great idea to have a (second) smartphone or pc screen without having a solid screen. The reason ...
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0answers
23 views

Stop CO2 laser firing through holes in glass

How would you prevent a CO2 laser with interlocks used to mark glass from firing if there were holes in the glass. Usually the interlocks prevent the laser from firing unless it is pressed against ...
0
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2answers
255 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 ...
0
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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 ...
7
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1answer
118 views

How legit is this paper claiming to have observed Hawking radiation? [closed]

I recently stumbled upon this paper. In it, the author claims to have found a signature for Hawking radiation in a condensed matter system. I know that experimentalists have been trying to find ...
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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 ...
4
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2answers
173 views

Spectrum of generic $\mathrm{CO_2}$ laser

It is often quoted, that it's emission is 10.6um. But we also know that CO2 lasers have huge number of possible emission lines in 2 main bands: 10.6um and 9.6/9.4um. But what is emission spectra of ...
3
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1answer
114 views

How to create a barrier for sound waves?

Is there a way to create a barrier so that sound waves cannot pass through? Does laser light have this ability to act as a barrier or bounce sound waves back? This came to my mind when I was ...
0
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1answer
44 views

Beam of electromagnetic wave, with radius of 3cm or less

I need to create a beam of electromagnetic wave, with radius of 3cm or less, for distance about few meters. What is the minimum frequency (maximum wavelength) that it is really possible?
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2answers
41 views

Lowest detectable power of a laser?

What is the lowest power of a laser beam which is still detectable? More precise: If the intensity of my laser beam is reduced by a factor of $10^{-8}$, can I still detect it? Of course this depends ...