Talk:Laser/Archive 6

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Archive 7

Spectral lines

I have also made the "laser spectral lines" diagram an SVG, and in the process I noticed that the original diagram mentioned a "ramen" shift for Nd:YAG! I also changed the axis text from "Wavelength - micrometres" to "Wavelength [μm]", and made the wavelength range blocks translucent. --Slashme 07:46, 18 September 2007 (UTC)

By the way, there's something strange in the chart: EI-YAG at 1.64 μm. I can't figure out what that's supposed to be. It could be a misprint for Er-YAG, but then it would also be the wrong wavelength. Any corrections welcome! --Slashme 07:59, 18 September 2007 (UTC)

More accessable intro

I think the intro should be more accessible to the average reader. The description can be more formal and technical later in the article. ike9898 15:45, 1 October 2007 (UTC)

• Seconded. E104421 23:44, 11 October 2007 (UTC)

Legality

what are restrictions for owning lasers,, what is the max power of a personally owned laser -- Gunnar Guðvarðarson 02:10, 22 October 2007 (UTC)

Military

It does not mention in this article that the military has developed lasers, mounted on jeeps, that are capable of slicing down incoming enemy fire in the form of missiles. It is infrared, therefore invisible to the naked eye, but is capable of great destruction. The army has stated they can not mass produce such a weapon, though, because of the high amount of energy it uses, and that it is too big for the field, at the moment. They do have a working version of one which they displayed on Future Weapons on the Discovery Channel. A seperate group is also working on a much smaller version.

Here we go, the THEL and Airborne Laser. There is no mention of these in the article that I saw.

Diffraction -> dispersion

Light seems to travel in rays, yet diffraction effects makes it seem like a laser (or any other light source) would spill out of its aperture as a spherical wave front. Obviously, that doesn't happen. Why does light appear to travel in rays whereas I can't imagine a "ray" of ocean waves; they would just disperse. —Ben FrantzDale 02:33, 2 November 2007 (UTC)

A shot in the dark. Consider that (1) lasers are often approximated as having Gaussian intensity distribution, (2) diffraction acts like a Fourier transform, and (3) an eigenfunction of the Fourier transform is the the Gaussian distribution. Perhaps a wave front with Gaussian intensity profile is exactly right to not disperse? (Or, more accurately, to disperse to form the exact same intensity distribution.) 155.212.242.34 13:53, 2 November 2007 (UTC)

That looks plausible, given the intro to Gaussian beam. —Ben FrantzDale 02:19, 4 November 2007 (UTC)

It helps that a gaussian beam is an eigenfunction of laser cavities that contain a focus, since lenses act as a fourier transform. All beams have some divergence (unless your source is actually infinitely far away), it's just possible to get it quite small with gaussian beams. — Laura Scudder ☎ 03:24, 3 February 2008 (UTC)

You are duplicating one of the early objections to the wave model of light, from Newton's day. Scientists of the time just couldn't imagine a wave (like an ocean wave) behaving like a "ray". It comes down to a matter of scale. Visible light has very short wavelengths compared to the objects we can observe. This tends to limit the effect of diffraction, so light in our ordinary experience appears to travel in straight lines. When one introduces changes in intensity across distances closer to the wavelength in scale, diffraction effects cause light to spread in the way that we are used to with other kinds of waves. You can indeed make a "ray" of ocean waves, if you arrange for them to travel through an aperture much larger than the wavelength and look at propagation over long distances (compared to a wavelength).--Srleffler (talk) 01:31, 9 April 2008 (UTC)

Eye damage

Does the potential for eye damage in lasers, such as laser pointers, exist in other situations as well?

For example, if someone were to look through a telescope aimed at the sun on an overcast day (during the day) with a UV index of 1, but the person had his/her eyes shut while doing it, would the person's eye(s) be damaged by the sunlight or UV rays? (As with a laser when it is shown at a person's eyes) Latitude0116 (talk) 19:43, 17 January 2008 (UTC)

I'm not sure if you're trolling, or just incoherent. One can damage one's eyes with concentrated non-laser light. You can burn things by concentrating the sun's light with a magnifying glass too. Same principle.--Srleffler (talk) 01:25, 9 April 2008 (UTC)

Thought it may be useful to note that in the US, the laser safety classification and identification is controlled by the FDA.--Caveman

The regulations Caveman mentions are easily accessible on-line but they require a bit of effort to interpret. The basic point is that the irradiance of light at the exit facet of a diode laser is in the neighborhood of 0.1 to 10 MW/cm2. NB: MW/cm2 stands for megawatts/square cm. The lens of one's eye is capable of focusing the laser beam that enters the pupil of the eye and can attain many kilowatts/square cm on the retina. It is enough to do damage. This analysis is only true for wavelengths at which the aqueous humor filling the eyeball is transparent; that is not the case for ca. 1450 nm and longer wavelengths.Jabeles (talk) 22:20, 28 July 2008 (UTC)

Revert intro

I am going to revert the intro (or at least the start of it) to the version of 4:59 March 4 2008. After that edit, the article was vandalized, and subsequent editors improved the vandalized introduction without reverting to the unvandalized version. The result was an intro that is inferior to the earlier version. Wikipedia articles should rarely begin with "The term x is...". Wikipedia is not a dictionary, but rather an encyclopedia. Wikipedia articles are about things, not about the terms that describe them. This is why things that share a common name have separate articles (with disambiguation), while things that have several names cover all of them in a single article.--Srleffler (talk) 01:05, 9 April 2008 (UTC)

In the revert, I am also restoring the footnote about "lazer" being incorrect. I am doing so not because I necessarily feel that this note is important, but because it was deleted in an edit that was misleadingly labeled as a vandalism revert. (The edit reverted a vandal, and also deleted a footnote that had been present in the article for some time.) I'm not sure whether the editor just made the change by the way and forgot to mention it, or whether it was somehow a mistake.--Srleffler (talk) 01:15, 9 April 2008 (UTC)

Citation - Australian Fines of $30,000

In the article there is a statement about fines of up to $30,000 and two years imprisonment, however a citation is needed for these. http://www.abc.net.au/news/stories/2008/04/11/2213837.htm this news article seems to repeat this information, and, for those not in the know, the ABC is one of the biggest news suppliers in Australia. 59.167.128.135 (talk) 04:02, 16 May 2008 (UTC)

With a single google search for "Australian Civil Aviation Act penalties" I was able to find their website. By using their site's search engine, I found these references:

http://casa.gov.au/media/2007/DOTARS07_136MV.htm and http://casa.gov.au/rules/1998casr/139/139c23.pdf

What I can't find is something referencing the $30,000 (AU) penalty, only the jail-time.

Jcaturia (talk) 06:36, 16 May 2008 (UTC)

Under heading 'Design'

Laser acronym:

'The word light in the acronym Light Amplification by Stimulated Emission of Radiation'

Should this not be laser.

OakeyDokey (talk) 08:13, 16 May 2008 (UTC)

No. There is no word "laser" in the acronym Light Amplification by Stimulated Emission of Radiation. Laser *is* the acronym. It's talking about the fact that the "light" is used as a generic for photons of any electromagnetic energy. Ttiotsw (talk) 08:30, 16 May 2008 (UTC)

136.182.158.153 (talk) 17:13, 16 May 2008 (UTC) Read this excerp: Has anyone brought up the acronym "LOSER" was a possibility until the full thought process took place and it was realized LOSER might not be a very good name after all?

In 1959, a year before anyone had built a laser, physicist Arthur Schawlow pointed out
that since the amplification is achieved by bouncing the photons back and forth
within a resonant cavity, the process would be better described as "light oscillation"136.182.158.153 (talk) 17:14, 16 May 2008 (UTC)

You need find a few reliable sources as references that says that. It sounds a bit fringe and apocryphal. Ttiotsw (talk) 20:08, 16 May 2008 (UTC)

It's true Schawlow said that, but this was after the acronym LASER was coined (by Gordon Gould). Schawlow and Townes preferred to call the device an "optical MASER". Schawlow was making fun of Gould's acronym. Gould's acronym stuck, however.--Srleffler (talk) 23:15, 16 June 2008 (UTC)

Spelling

Why does an article about a technology developed by U.S. scientist in a U.S. laboratory use British spelling (e.g., colour)? Moretz (talk) 23:51, 16 May 2008 (UTC)

The word "colour" isn't used actually though the word "coloured" is used, once. Any other examples you want use to consider ? You're going to have to be a lot more precise if we're going to start bending Wikipedia conventions. Ttiotsw (talk) 11:04, 17 May 2008 (UTC)

Because the technology is not particular to the U.S., despite having been developed by several U.S. scientists in several U.S. laboratories.--Srleffler (talk) 23:12, 16 June 2008 (UTC)

... and because the article was originally written with British spelling, though I note that someone has changed it to American! (I'm not particularly worried, I can read both!) Dbfirs 08:57, 17 June 2008 (UTC)

... (later) ... I was wrong above. The original article was written by a British Wikipedian, but he used American spelling (presumably as per WP:ENGVAR. So all is as it should be. Dbfirs 09:20, 17 June 2008 (UTC)

Typo

please replace "axample" with "example" in the first few paragraphs. page is locked, can't edit. —Preceding unsigned comment added by 76.85.197.200 (talk) 04:19, 17 May 2008 (UTC)

Done [1] but slightly tweaked as well. Ttiotsw (talk) 11:07, 17 May 2008 (UTC)

Acronym

If laser is indeed an acronym, why isn't it written in caps, like SONAR and RADAR? DRosenbach ^{(Talk | Contribs)} 13:48, 3 June 2008 (UTC)

It probably was, but like sonar and radar, the term has become an ordinary word, even to the extent of the back-formed verb! Dbfirs 14:13, 3 June 2008 (UTC)

Yes, but...doesn't that still make it technically incorrect? As such, should be capitalised in the article of an Encyclopaedia? Not trying to beat a dead horse, just pointing out, that while "RADAR" may be written "radar" in casual English, Wikipedia is a formal area of writing, and the grammar should reflect that. It's a relatively major change, considering each usage of the word LASER would need to be capitalised, but given an hour or so it shouldn't be to difficult does anyone else have a more efficient way of doing this, or volunteers to replace the word instances? Neuro√Synapse ▪ ∆ 08:05, 20 June 2008 (UTC)

No, it doesn't make it technically incorrect. Language evolves with time. "Laser" has long since evolved into a word. It no longer matters that it was originally an acronym. The issue is more than just casual English—laser is not typically written in all caps in the technical literature either. You wouldn't find a modern laser physics paper where the authors use "LASER".

If you like, you could think of "laser" as an English word distinct from the acronym "LASER". A LASER is a device based on light amplification by stimulated emission. A laser is a device that lases—that is, it emits coherent light due to oscillations fed by stimulated emission. The acronym "LASER" is not even technically correct. Nobody would call an optical amplifier a laser, but it is explicitly a device that uses stimulated emission to amplify light. The key defining characteristic of a laser is that in addition to amplification by stimulated emission it has feedback sufficient to produce oscillation.--Srleffler (talk) 22:02, 20 June 2008 (UTC)