what’s the difference between a laser and a light beam?
how is a laser beam created?
they’re different things, but at the same time they’re pretty much just light, so it puzzles me
Laser light is coherent; it’s the same wavelength.
To more specifically answer your question, a laser is not as spread out as light (regular photons).
^^That’s a really short answer, plenty more folks will expand on this i’m sure
Put simply, laser light has two main features:
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It is extremely pure in frequency (color)
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It’s “point source” light; it seems to radiate from an infinitely
small spot.
(advanced users call these “temporally coherent” and “spatially coherent.”)
Most explanations of laser light have some serious problems, especially with #2 above. For example, there is no such thing as “in-phase light.” Light from point sources takes the form of sphere-waves or plane-waves. Laser light is the very opposite of “extended source light” such as a glowing panel. So, tiny light bulbs are closer to laser-style light, and big wide fluorescent fixtures are farther away. Also, laser light is not paralell light. Inspect any diode laser and you’ll find a lens in front. The diode emits spreading sphere-wave laser light. The lens brings the spreading light together into a parallel beam. In fact, even HeNe tube-type lasers emit spreading light, and they always have a little lens glued onto the front in order to form the light into a parallel beam.
To change light-bulb light into laser light, just pass the light through a color filter which rejects all but a single frequency of light, then pass the light through a tiny pinhole which converts the colored light into pure sphere-waves. Since both of these reject most of the light, any light you get is ridiculously dim. Dennis Gabor, the inventor of holography, actually did this. He made crude but successful holograms many years before lasers were invented by using gas discharge tubes with narrowband filters and passing the light through a pinhole.
SOME LASER MISCONCEPTIONS
http://www.amasci.com/miscon/miscon4.html#phase
When you say “beam” would that be like a ray? Would there be a certain era of rays in particular that you want to know about?
[sub]There’s the set-up, folks.[/sub]
Laser material is fluorescent. After something “charges it up”, it glows for a brief time. But more importantly, its fluorescence can be triggered prematurely when light shines upon it. Charge it up and it glows dimly (this is called Spontaneous Emission). Then shine some external light on it, and it glows very bright (called Stimulated Emission.)
There are two basic ways to make a laser:
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Use a very, very very long rod of laser material which lacks any mirrors.
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Place two mirrors facing each other to form an “infinite tunnel” effect, and then put a short rod of laser material between them.
Laser materials are very weird. They amplify the light which passes through them. And because they are transparent, they preserve images which pass through. They’re like backwards sunglasses, where everything would look brighter rather than dimmer when wearing them.
Another way to look at it…
What happens when you have an audio amplifier, and you hold the microphone too close to the loudspeakers? The amp becomes an audio oscillator. Sending the same noises through the amplifier over and over will strip away all but one pure tone, and that tone becomes very loud. The same thing happens to light which passes through laser material. A laser is an “optical oscillator.” And not only does it put out a very pure “tone”, it also puts out a very pure image: the image of an infinitely tiny point.
Winston Kock of Bell Labs, one of the early laser researchers, noted that laser light is “sharper” than normal light. If you focus the light from an everyday light source such as a clear light bulb, you get a small upside-down image of the source. But if you focus laser light, you get the image of a single point, so the bright spot is much hotter than the spot made with a normal light source. If we could concentrate the output of a 100 watt lightbulb into a spot a few hundredths of a mm across, then light bulb light could cut steel. Because light-bulb light carries the image of a light bulb, we cannot do this. Arc lamps have smaller source size than a hot filament, so a focused arc lamp approaches lasers in intensity. But still it falls short. Laser light is a sharper tool.
It’s a laser beam if it is a beam coming from a laser. Some lasers such as laser diodes don’t produce a beam as much as they produce a cone of light, and they need a lens to focus this cone into a beam (this is called “collimating” the light).
And something is a laser if it uses the amplification effect that some materials have, wherein a photon of light passing through the material tends to trigger the release of another photon having the same wavelength and direction, and the same phase (the wavefronts are in step wtih each other).
Lasers differ in how perfectly true it is that the photons have the same wavelength and phase and direction, but it is so much truer of lasers than it is of other light sources that practically they are in a class by themselves.
Coherent amplification is a property of electromagnetic radiation, not confined to visible light. The first device was a MASER, using microwaves in place of visible light.
There are now infrared lasers, ultraviolet lasers, x-ray lasers, etc.
... prematurely......spontaneous emission....This laser business is really *sexy!*
V
In the old days, more that 35 years ago, the shop apprentice was sent to get a ten foot length of ‘english’ channel. Now he is sent for a length of laser ‘beam’ ten feet long! 