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.
Questions tagged [laser]
1648 questions
314
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What is Chirped Pulse Amplification, and why is it important enough to warrant a Nobel Prize?
The 2018 Nobel Prize in Physics was awarded recently, with half going to Arthur Ashkin for his work on optical tweezers and half going to Gérard Mourou and Donna Strickland for developing a technique called "Chirped Pulse Amplification".
In general,…
Emilio Pisanty
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158
votes
1 answer
What is an "attosecond pulse", and what can you use it for?
The 2023 Nobel Prize in Physics was announced today, and it was awarded to Pierre Agostini, Ferenc Krausz and Anne L’Huillier, for
“experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter”.
The…
Emilio Pisanty
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153
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2 answers
Why does a mirror split my laser beam?
Last night my daughter was asking why a mirror "always does that" (referring to reflecting a spot of light). To help her figure it out, I grabbed my green laser pointer so she could see the light traveling from the source and reflecting off the…
Wayne Werner
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How do laser "tape measures" work?
There is a device available for about $\$40$, which fits in the palm of the hand, runs on two AA batteries, and can measure distances up to $50\,{\rm ft}$ to an accuracy of $\sim \frac{1}{8}''$ ($\sim 3\,{\rm mm}$).
Light travels $300,000\,{\rm…
Anthony X
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91
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2 answers
Why is a laserpointer able to "erase" a glow-in-the-dark sticker?
a while ago I tried to charge a glow-in-the-dark sticker using a simple red laser pointer. It was a large sticker, of the type used to mark emergency exits and fire extinguishers here in Germany. I thought I could draw a picture this way, with…
Toastor
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72
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2 answers
How to measure the wavelength of a laser pointer?
I'm working on something and I need to know the wavelength of the laser pointer that I'm using.
Can you suggest me a way, using some optics formulae, or anything else to calculate the wavelength?
user82920
49
votes
6 answers
Why do lasers cut? Is this a case of light acting as matter?
All I found in Google was very broad. From a physics models perspective, why can photons emitted from a laser cut? Does this cut mean that the photons are acting like matter?
sites
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43
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7 answers
Three polarizers, 45° apart
If light is passed through two polarizing filters before arriving at a target, and both of the filters are oriented at 90° to each other, then no light will be received at the target. If a third filter is added between the first two, oriented at a…
vaindil
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43
votes
3 answers
Is it really possible to break the speed of light by flicking your wrist with a laser pointer?
Minutephysics has a popular YouTube video called "How to break the speed of light". In the video it states that if you flick your wrist while pointing a laser that reaches the moon, that the spot of light on the moon will travel 20 times the speed…
miguel.martin
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41
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2 answers
Why does laser light not affect glowing materials?
I have this childrens rubber ball which glows in the dark after it's exposed to light. I "charge" it with a flash light then play with my dogs at night. I thought to try a very intense green laser, and see how the ball reacted.
The laser light had…
Michael
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36
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2 answers
How well can a laser be focused over interstellar range?
I try to read up on diffraction limiting and gaussian beams, but it always gives a result saying it’s characterized by an angle which is the edges of a cross section of a cone. Which says nothing on the physical limits of how I choose that angle. …
JDługosz
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35
votes
5 answers
Do free-electron lasers actually lase?
Free-electron lasers are devices which use the motion of highly energetic electron beams to produce bright, coherent radiation in the x-ray regime. More specifically, they start with a high-energy electron beam and feed it into an undulator, which…
Emilio Pisanty
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34
votes
5 answers
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 effect?
Gouy predicted and then experimentally…
nibot
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29
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2 answers
How does a laser from Earth manage to hit the Moon with precision?
A question I've been asked is how a laser, fired from earth, would hit the moon without "leading it" (or hit it with precision). When firing a laser at the moon, it takes about 3 seconds to reach it. Given the combined effects of orbit, rotation,…
Omnivore
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28
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What if we shine a laser to east and another to west, will they arrive at the same time?
If we have two lasers based at the equator and we direct one of them east and the other west on to two screens each 10 km away, will light emitted synchronously at the lasers arrive at the same time as each other on thier respective screens?
My…
RendezvousRama
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