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In comments on Would a laser weapon visibly fire?, it is claimed that the majority of devices sold to consumers as lasers are, in fact, LED-based. I think that (at least in the US), laser devices up to a few milliwatts power are legal and inexpensive. For instance, I own this device, which I believe to be a laser. Is it? More generally, are real lasers available for purchase to consumers for less than, let us say, $100US?

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Larry OBrien
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    And what would it cost to attach _real_ lasers to the heads of sharks... – Flimzy Feb 13 '12 at 02:33
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    There's an easy way to tell whether a device that produces a beam is a laser or not. Lasers and _only_ lasers produce _speckle_, where a spread-out dot appears not uniform in brightness but swirly patterns of light and dark just barely visible; furthermore, this pattern changes as you move your gaze even when the spot stays still--this is interference on your retina of the coherent laser light. LEDs (and incandescent and fluorescent lights) are not coherent and thus cannot produce this effect. – Rex Kerr Feb 13 '12 at 04:06
  • @RexKerr Also worth noting is that the noise pattern is _not random_ - that is, when I move my head, I can definitely see that I am looking at a different part of the same pattern, and it does not (with a steady hand on the laser) change over time. I'd always assumed it was interference on the target surface rather than the retina - does this phenomenon have a name so I can find information about it? – Random832 Feb 13 '12 at 14:42
  • Incidentally, I am also skeptical that there are things "sold to consumers as lasers" that are not lasers - I don't doubt that LED pointers exist - I mean, that putting the word "laser" and a warning label on a product that does not contain a laser is A) legal and B) ever actually happens. – Random832 Feb 13 '12 at 14:54
  • @Random832 - Check out http://en.wikipedia.org/wiki/Laser_speckle (especially the subjective speckle section). Note that the relevant "image plane" for your eye is your retina. (I'm sure there's something better, but hopefully that's adequate.) – Rex Kerr Feb 13 '12 at 16:50
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    This is dangerously near General Reference territory. Laser Emiting Diode (the basis of laser pointers) have been around for a long time now and are also used in consumer electronics, supermarket checkout scanners and many other places. They may (especially if cheap) have poor qualities in terms of beam spread and coherence length which makes them unsuitable for some classroom demos but they are still lasers. – dmckee --- ex-moderator kitten Feb 13 '12 at 17:05
  • @dmckee - I've never seen any consumer device that did not generate visible speckle when examined carefully (e.g. shining a spot on a sheet of paper). They might not be suitable for a classroom demo, however. – Rex Kerr Feb 13 '12 at 17:59
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    In what way are LED devices not lasers: the question implies you can't be both. Most devices are low-power LED lasers. – matt_black Feb 13 '12 at 21:34
  • @matt_black The original claim is "most things sold to consumers as lasers aren't, they're merely LEDs with a collimator lens in front of them" As you say, implying they can't be both. Additionally, is it common to refer to a laser diode as an LED? – Larry OBrien Feb 13 '12 at 22:41
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    They are both LEDs and lasers: "A laser diode is an electrically pumped semiconductor laser in which the active medium is formed by a p-n junction of a semiconductor diode similar to that found in a light-emitting diode." https://en.wikipedia.org/wiki/Laser_diode – endolith Mar 04 '13 at 19:36

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All the laser pointers I have seen, are in fact lasers. It's easy to tell, If you point one at a wall about 20 feet away, it will create a very small point of light, a few mm across. If you do that with a LED light, the beam, if it's powerful enough will be anywhere from half a meter to a meter in diameter. Only a laser can keep a beam that tight.

The device you link to is a real Laser

There are laser Diodes, which might be the source of the LED comment. Here are some commercially available laser diode modules.

Small, inefficient lasers are cheap. They're used in DVD players, CD players, bar code readers, and in the mouse I'm using.

Larry OBrien
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Nthaoe
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The device you have is a real laser pointer, with a wavelength of 532nm and an output power <5mW - and I can pick one up for $70 or £50. You can also get ones with a power output of up to 1W for personal usage - as this one proudly states.

They are widely available in the US and the rest of the world, so relevant legislation for you in the US is as follows (from Wikipedia):

  • Laser pointers are Class II or Class IIIa devices, with output beam power less than 5 milliwatts (<5 mW). According to U.S. Food and Drug Administration (FDA) regulations, more powerful lasers may not be sold or promoted as laser pointers.
  • Also, any laser with class higher than IIIa (more than 5 milliwatts) requires a key-switch interlock and other safety features.
  • Shining a laser pointer of any class at an aircraft is illegal and punishable by a fine of up to $11,000.
  • All laser products offered in commerce in the US must be registered with the FDA, regardless of output power.
Rory Alsop
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