Talk:Laser/Archive 1

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This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

This page contains archived discussion from Talk:Laser with the last contribution dated before Jan 1, 2006.

Reorganization

Starting to reorganise, splitting laser from laser applications.

Follow section removed, since it's covered in laser applications:

These properties have many uses in science and technology. (Please list some here as links.) Alternative light sources with all these properties are typically weak and cumbersome. Lasers are widely used by the armed forces in many applications. Lasers can be set to specific, pre-determined frequencies to correspond with a bomb or missile's tracking system. Because the frequency can be set to a range not normally found in natural light settings it is easy for a homing device to find and home in on the signal. Also, lasers can be mounted to weapons and collumated to line up properly with the barrel for targeting purposes. This is especially useful in night combat environments. Some lasers are not in the visible spectrum, and can only be seen using devices that can see infrared, allowing easy targeting for users utilizing night vision devices.

-- DrBob 2001-09-25

Rewritten, to remove redundencies and improve flow -- DrBob

Thanks DrBob. The whole rewriting process in the last few weeks has been great. Geronimo Jones (original author).

Radio lasers?

Can you enlarge on the early "radio lasers" prior to masers? Have you got a reference, a name, anything? This sounds fascinating... The Anome

Ho:YAG/Nd:YAG

The hospital I work at uses Holium YAG in the OR for laser surgery (cutting/coag). Is this the same as Nd:YAG or similar? If it is a seperate type of laser, should it be included in the list? Perhaps even in Laser Applications since it is used for surgery? We use other lasers in the OR as well, but the YAG/Holium is the newest. Nurses like it better then the others because it is smaller, easier to transport and can take more abuse without decalibration issues. Appearantly the larger lasers we use can be decalibrated easily if bumped. I'd love to see a section or article on comparisons of lasers and their characteristics. Specifically regarding application. And diagrams would also be a place for improvement. Keep up the good work. Robert Lee

Ho:YAG is has the same host material as Nd:YAG (YAG=yttrium aluminium garnet), but a different dopant material (holmium instead of neodymium), see information about this in laser construction. This makes it operate at a longer wavelength (2.1 microns instead of 1.06 microns). Probably the best place to add stuff like this is in laser applications. Specific laser information has been on my "To-do in my copious free time" list for a while. -- DrBob 2002-11-17

Laser safety

A while ago, an anomymous user made a number of changes in the laser safety classification. The result sounds professional with lots of numbers, but does not agree with what I remember learning in laser-safety instructions. The previous version is what I originally wrote, mostly based on my memory and what I could find on the web.

class I: laser pointers? I was pretty sure that laser pointers are Class II or IIIb, though the latter is controversial because of the associated eye hazard. Class I would give a spot that noone[sic] can see and class IIIa would be too big a spot size.
class II: the lower end of the power range, .39 uW, sounds way too low for visible light (400-700 nm).
class IIIb: it should be "unsafe for the eyes if the beam enters the eye". The phrase frequencies 315 nm to 1 million nanometer (sic) does not sound very scientific. The upper limit of 500 mW is also unrealistic it would be more like 5 mW.

I will revert.

-- Hankwang 09:40, 23 Apr 2004 (UTC)

PS, can everybody please timestamp comments? I added a few.

Definition of a laser

Someone want to elaborate on the reason for using collimated as part of the description of what constitutes a laser—the output from a laser diode is not generally regarded as collimated but everyone agrees they are lasers :-) --lidarman 05:37, 28 Apr 2004 (UTC)

Likewise there are other lasers that aren't particularly coherent or monochromatic, but everyone agrees they are lasers. The problem comes with fitting a one-line common definition to all the variety of the real thing. I'd say leave the description intact but if neccessary clarify further down -- DrBob 15:57, 28 Apr 2004 (UTC)

As I see Hankwang has already done, thanks -- DrBob 16:01, 28 Apr 2004 (UTC)

Even HeNe classroom lasers naturally produce spreading light (due to confocal resonator.) Manufacturers typically add a lens to the output end of the laser tube in order to collimate the beam. Hmmm. Do ANY modern lasers produce collimated light (i.e., use large parallel flat mirrors?)

So what IS a laser? An optical oscillator using a gain-medium? Winston Kock called lasers "sharp tools," since lasers differ from other sources in that their light can be focused to nearly a geometrical point. --Wjbeaty 06:11, Mar 31, 2005 (UTC)

The definition is in the name, any device that uses "light amplification by stimulated emission fo radiation" is a laser. Or are there any devices using this that "everyone agree not to be lasers"? -GalFisk [not logged in]

The "light amplification..." phrase could also apply to image intensifier devices. (SEWilco 16:54, 30 August 2005 (UTC))

My professors used to say that the more correct name for the device would be "light oscillation by stimulated emission of radiation", but nobody likes the acronym. That name would maintain the requirement that stimulated emission be part of the operating mechanism, but would rule out image intensifiers and other devices that don't produce a coherent oscillation.The Photon 15:35, 11 October 2005 (UTC)

Diffraction?

The beam will eventually spread due to the effect of diffraction but much less than a beam of light generated by other means.

I don't see how this could be diffraction, since it would occur in empty space. anthony (see warning) 03:41, 20 Aug 2004 (UTC)

Diffraction is usually thought of as happening when light hits a slit or some other obstruction, but it also occurs for any beam of finite size propagating in free space. For this reason, you can't focus a beam of light into a spot of infinitly small size, or make a beam which is perfectly collimated.

If you don't like the idea of diffraction in free space, you can think of the laser beam's inevitible[sic] spreading as occurring due to diffraction from the last aperture the beam passes through (e.g. the output coupler mirror of the laser). -- DrBob 15:59, 20 Aug 2004 (UTC)

Well, yeah, I certainly agree that the phenomenon happens I just never heard it referred to as diffraction. Maybe the problem is the term "eventually"? I mean, yes at some point there is diffraction occurring, but this happens at the beginning, not at some point in the future. I'll try to reword without "eventually" I guess. anthony (see warning) 19:26, 20 Aug 2004 (UTC)

The word "eventually" should probably still be used. A collimated beam is not immediately changed to diverging at a certain angle after leaving the lens... there is transition distance in which beam waist varies non-linearly. At the lens, a collimated beam actually is collimated, with an infinite radius of curvature. Then the radius of curvature drops quickly over a relatively short distance, then approaches a fixed constant angle asymptotically. The radius is always positive anywhere away from the lens for a collimated beam, so the beam waist is expanding with distance from the lens, but right at the lens it is infinite.

A perfectly collimated beam cannot be created, due to the effect of diffraction, but a laser beam will spread much less than a beam of light generated by other means.

I think that's more clear. But feel free to reword further. anthony (see warning) 19:32, 20 Aug 2004 (UTC)

Safety issues

Re RPaschotta's addition, safety issues (even knowledgeable operators should not breach safety regulations!)

On paper these regulations sound wonderful, but I wonder whether you have ever tried aligning a Ti:sapphire laser or parametric amplifier with "adequate protection". I dare to say that that is impossible.

These devices are designed such that you cannot get any unexpected reflections during normal alignment, except if you remove parts that have big yellow stickers on them warning you that they are there for protecting you.

Han-Kwang (talk) 20:11, 20 Oct 2004 (UTC)

Severe or permanent eye damage my arse. I shone a laser pointer into my eye for half a minute, on two occasions, without suffering harm. I saw a yellow spot for a while, and had a little dizziness, but they disappeared. Though I wonder if astigmatism had to do with it... What happens when the dopant is removed from the laser? Why aren't there any diamond lasers? lysdexia 02:59, 21 Oct 2004 (UTC)

If it was a class I or II laser pointer, you're not likely to do that much damage (though deliberately staring at a class II is a very bad idea.) Class III and above, I assure you that permanent damage is quite possible (I know people who've suffered retina damage from less than a second of exposure to a class IV beam). Note the human eye and brain is quite adept at glossing over holes in your visual field, so you can be damaged and not know it.

If you remove the dopant from a solid-state laser, you don't have a laser anymore, since it's (usually) electronic transitions in the dopant ions that cause the laser action. If you remove the erbium from Er:glass, you're left with just glass. If you remove the Nd from Nd:YAG, you're left with a fairly boring transparent garnet (YAG) crystal.

Diamond, I believe, isn't very suitable as a host material because it consists of strongly-bonded light atoms (carbon). That tends to cause fast non-radiative (non-light producing) decays from higher energy states, which isn't good for efficient laser action. -- DrBob 04:37, 21 Oct 2004 (UTC)

Nope, I don't know of any class I or II pointers. They come at IIIa and IIIb, and the one I used was the commoner (guess). A physicist saying "quite possible" doesn't give one any brownie points with me. Anyway, you're probably wrong. IIIa's are <5mW. Even Sam's Laser FAQ cites a study that no permanent eye damage occurred from staring at IIIa's for half an hour. My eyes are more damaged—sometimes-dehydrated, I guess—from long hours at modern, large computer screens than any puny laser. *sigh* I could look at my old 11.5" screen almost forever. Can you give a test for hole blindness? There are diamond LEDs. Ooh, can one make a sonic aser from a diamond sample? :) lysdexia 21:25, 20 Dec 2004 (UTC)

I edited the safety stuff again in the new article laser safety and also gave some explanations on the corresponding talk page.

Following the comments by Han-Kwang: Indeed I have aligned Ti:sapphire lasers. Only during the very first stage where the fluorescence is used for a sort of pre-alignment, I had to take the glasses off. This was with the cavity blocked (so for sure no Ti:sapphire lasing) and after checking that no pump light was leaving the case. Concerning parametric amplifiers and oscillators, we have built quite a few of those in my research group at ETH Zürich, partially with very high output powers, and never had to use unsafe practices for that.

Anyway, physicists are used to solve many technical problems, so why shouldn't they be able to solve safety problems as well? With a little thinking, and sometimes some investment of time and money, one normally finds reasonably safe methods.

Besides, anyone is free to accept additional risks for himself. Recommending unsafe practices to others is another thing, which for obvious reasons I strongly recommend to avoid.

RPaschotta 12:16, 30 Oct 2004 (UTC)

Removed parts

I removed this:

A new state of energy, called liquid light, has been found in intense beams propagating through nonlinear optical media, whose electric and magnetic fields alter the refractive index of the medium, an effect called self-focusing, to condense the photons into an ultralow- divergence beam. Such a beam may have an indefinite range, and may eventually be focused to extragalactic distances without significant loss.

Liquid light sounds like pseudoscience and is not documented (nonexistant[sic] article). Self-focusing is a true effect but it only happens while propagating through certain materials, not while propagating through empty space. Focusing and losses are two completely independent things.

Also removed (context: laser projectiles in Star Wars):

Of course, this assumes that what we see is the actual laser beam, rather than a second, retarded effect such as turbulent atmospheric fluorescence or phosphorescence, or particle creation and decay.

The issue is whether you would see a flash of laser light propagating at a few 100 km per hour. The effects above would only affect the duration of the afterglow.

It's only nonexistent on Wikipedia. If that's your criterion for determining what exists, then maybe you should be out of work. I pulled the material back and rewrote it, bulldozing over your ignorance of new physics. (I'm occasionally amazed at how professionals and other authorities are so out of the loop.) Loss can apply to intensity as well: Being able to send a small-enough wavelength beam of enough intensity, one can—I suspect—still maintain a nondiverging beam in space, which is NOT EMPTY!

Laser light can propagate at any velocity. Get with it. Oh, and I'm not too happy about the people who downplayed laser projectiles. After I wrote my rough essay Making Stargate a Reality, I enjoyed finding news stories that confirmed my wishes, dreams, and claims, especially published after my essay was written. If Stargate is fiction, then why do images from the articles I just put in the laser article look just like zat beams or Asgard transporter beams and Gou'ald ring transporter beams? :) I need to get back to that message board to rewrite that essay, deleting a couple of calcuotypos and putting in real isotope decay chains with their outputs... I think substituting the kilometre there for a metre makes the temperature make a lot more sense. :D

For interested parties, here are a few of my feedbacks to Sam's Laser FAQ (I've posted on Scitoys too, and corrected the host a few times!):

Pressure of Light http://repairfaq.ece.drexel.edu/sam/laserioi.htm#ioipol

About your brief pressure of light section, I'll let you in on a little secret to make dreaming funner. The tiny force from a given energy or power light is only due to light's huge speed: That from a massive object at a normal speed would be much larger. People forget that when light is absorbed by any medium (diaelectret, conductor, superconductor, etc.) it acquires a mass and a noncelerity speed given by the medium's refractive index multiplied by celerity. So find a substance with a high-enough refractance, and absorbance, and it will experience a much larger force. With the "infinite" refractive index of atomic- or partonic-degenerate condensates, or black holes, an object may behave like it's reacting off an infinite-mass propellant to be effectively "pushing off space" as some bogus propulsion designs claim. I don't have the equations for this, but I suspect it's right. In order to make a more efficient tractor beam, the subject then must be put into a "condensate sabot". This is only one of dozens upon dozens of breakthrough ideas I've had in the past three years, along with those that allow futuristic scifi devices to work or be understood today.

Ring Lasers http://repairfaq.ece.drexel.edu/sam/laserioi.htm#ioiring

Why must resonators have integer half-waves? Like, couldn't one eliminate the regular minima and nodes by adding a large, high negative harmonic and antiwave, storing /that/ in the resonator, then removing the antiwave when the output is needed?

Wavelength versus Frequency http://repairfaq.ece.drexel.edu/sam/laserioi.htm#ioicav5

Maybe light is given in wavelengths instead of frequencies because the former is easier to grasp and the latter is quite large, not to mention a derived property. At RF, more attention is given to the oscillator than its dimension, though both are common. Hmm, I think I want to abolish frequency from all kinds of serious conversation or discussion: We don't talk about the reciprocal of wavelength, or resolution, do we? (Extending this proposal I'd get rid of gauge, mesh, fine, and grit.) It makes more sense to talk in fundamental properties, so instead one would give the period—the stint—of the wave as a little time for most wavelengths. Now that the frequency f or nu is gotten rid of, light's equation becomes simply and easily c = (l/t)_c. Most times may be tiny, but that's how they are. Because I also want to spurn (abolish!) Latin, the terms in English become swiftness = span/stint, or w = p/t.

-Aut lysdexia 21:25, 20 Dec 2004 (UTC)

Mist

"Some action movies depict security systems using red lasers (and being foiled by the hero, typically using mirrors); the hero may see the path of the beam by sprinkling some flour in the air. It is actually easier to build infrared laser diodes than visible light laser diodes, therefore such systems have no reason to work in visible light."

I've seen this done (in movies) with mist (a fine mist from a spray bottle)---where the laser was 'supposedly' not infrared. Is there a liquid that can glow in the presence of infrared which will make a fine mist like water can?

Anon (207.65.110.121) 13 Nov 2004

There are (expensive) dyes that you can "charge" with visible light (like the hands on your watch) that will light up when illuminated with near-IR light. You'd have to charge the contents of the spray bottle a few minutes beforehand and I doubt that the light would be bright enough to see. Han-Kwang (talk) 19:33, 14 Nov 2004 (UTC)

- I would really like to see these dyes. Are they multiple photon absorbing? I guess they'd have to be otherwise you're creating energy; light emission is always red-shifted (lower in energy) from the excitation. It can theoretically be the same wavelength, but every lumophor I've seen has a stokes shift. By implication they are also phosphorescent (like the hands of a watch) which can not emit light that is not red-shifted because the process involes an exothermic internal conversion to the triplet state. At any rate, can you provide a link or something? I'm very curious how you can convert near-IR light into visible light by phosphorescence... Fearofcarpet 18:06, 18 Mar 2005 (UTC)

I haven't actually encountered this sort of dye, but I would imagine that the "charging" operation is to put the dye in an meta-stable excited state such that absorbing an infrared photon causes the state to decay and emit a visible photon. --Carnildo 21:00, 18 Mar 2005 (UTC)

"Needs attention"

I listed this article on Wikipedia:Pages needing attention because I think the most recent round of edits could be better integrated into the article. Nothing horribly wrong, but some more eyes looking at it couldn't hurt. Gwimpey 04:50, Dec 21, 2004 (UTC)

Sorry but don't like this "liquid light" stuff

I removed the paragraph[] "In 2002, a Spanish research team led by Humberto Michinel came up with computer simulations showing intense beams sent through special nonlinear optics, whose electric and magnetic fields made a concentric refractive index gradient in the medium as seen in normal self-focusing, but were slightly slacked in the beam's core to prevent a convergent-divergent beam from forming. The result was their discovery of a new state of energy, liquid light or light condensate, obeying viscous fluid properties such as surface tension and vorticity, whereby the beam could be split into drops and droplets if it hit a surface. [1] [2]"

from the article for 2 reasons. First, it is an entirely theoretical hypothesis and has never been observed in a laboratory experiment. Second, this is a general article on lasers and a buzzwordy unproven cutting edge hypothesis does not belong here. Also, I tend to strongly doubt its relevance and or importance; it's been like three years since this paper came out and I've heard nothing else about it. That, to me, = dead end minor curiosity in a backwater of laser research not "fundamental breakthrough". --Deglr6328 19:49, 21 Dec 2004 (UTC)

I did not word it to claim that it was a shown and known entity. Read more carefully. It was part of the beginning sections supposing the properties of different light beams. The idea to put in liquid light followed from the filament which was found much earlier, yet you kept that in. Why? Different forms of a laser beam are relevant. The discoveries that inversions weren't needed to lase were much longer ago, and I doubt that you heard anything about it; if so, why wouldn't you or other laser experts write about it, and keep claiming that inversion is part of lasing operation? Whether or not you heard of something doesn't determine whether you keep something in an article. And it's only been two-and-a-half years, not three. More time passed before the second time noninversion lasing was seen and reported again, which you apparently missed also. lysdexia 22:43, 21 Dec 2004 (UTC)

Stop editing the talk pages with your grammar "corrections"! You've been warned about this many times and I've added my name to the consenting opinion on the request for comment page about you. --Deglr6328 22:21, 21 Dec 2004 (UTC)

The page includes the Wikipedia variance that talk pages are fair game. If you were more familiar with reality, you wouldn't be complaining. If you don't want to be corrected, write correctly. lysdexia 22:43, 21 Dec 2004 (UTC)

I see now you're in the habit of removing my comments from the talk page? --> "The filament mentions are experimentally proven phenomena and are commonly known and used. The "liquid light" term dubbed by press release phenomenon is not even proven. It dosen't belong here. Also to call it a "new form of energy" is insanely pseudoscientific."--Deglr6328 22:21, 21 Dec 2004 (UTC)"

I've had enough of dealing with your nonsense. You're so close to being listed on an arbitration page.--Deglr6328 22:51, 21 Dec 2004 (UTC)

What did I remove? You didn't even finish that quotation. I never called it a new form of energy. Why can't you read right? Why don't you ever try to argue back instead of making threats that have no bearing? lysdexia 23:47, 21 Dec 2004 (UTC)

That was a slip of the cursor, an accident. I'm still waiting for you to answer my above. lysdexia 23:59, 21 Dec 2004 (UTC)

YOU deleted the answer! And now you're ignoring it! I think we're done here. Also there is nothing "choppy" about the way the article was left relative to what it was before, I've merely consolidated sections talking about quantum effects etc. --Deglr6328 01:01, 22 Dec 2004 (UTC)

I expanded the above just after your answer. Don't you notice it's a lot longer? Both parts of your "answer" weren't enough. If the filaments were known, why was there never any mention of them with divergence? Yes, it's choppy now. The starts and ends of those paragraphs no longer match or flow, your image is in the wrong place, you removed emphasis on nonlinear exceptions, chirping and filamenting are unrelated, you removed the fact of a turnaround, you put needless emphasis on higher powers and a personal assumption of deadliness, you left the lie and red herring that shows always and definitely used lasers, you left the false assumptions in the same section, you detracted from the stated purpose of the section, you orphaned references, and most importantly you degeneralised your "general article" claim. lysdexia 03:51, 22 Dec 2004 (UTC)

What are you talking about!?! Ugh, you're so incomprehensible most of the time I can't even decipher your complaints. CPA and filamentation ARE related, you NEED to use CPA to achieve the fluences necessary to start kerr lensing and 'filamentation' in air, again if you knew something about lasers you'd know this. And the image is in exactly the right place, right next to talk of CPA which introduced a huge increase in pulse powers. And how did I "orphan refrences"? --Deglr6328 05:29, 22 Dec 2004 (UTC)

I'm only "incomprehensible" to you. This is your only excuse for not answering me. You pasted lines from other paragraphs into new paragraphs, where they didn't belong. Do you not understand what start and end mean? My main problem with your change, in the beginning section, was that you didn't allow or played down the qualification that light beams behave differently than that commonly claimed in popular or even technical literature. What you said here wasn't written there, but they are still unrelated because chirping is only one way of filamenting, just like how I needed to write in that inversion is only one way of lasing. You have problems understanding causality and necessity. You cannot find anything to support your "NEED"ed claim. Look where I put the image in my edit. It belongs there with all the lasers. You tell absolutely no connection between that image and section, and only a minor part of the image is relevant there. I think you also removed where I put 30 GW as the air threshold, and you put in terawatts twice, still being unrelated to the filament section, which was fine when I put it in. The article is very choppy now; it's top- and bottom-heavy. The references no longer correspond with the article's content. In your edit summary, you thought I wrote reverting when I wrote rewriting. You put in a wholly-needless section on uses when there already was a separate article for them. With all of your misspellings and understanding problems, maybe you've spent enough time with bright lasers. lysdexia 03:39, 29 Dec 2004 (UTC)

Put the disputed paragraph on a new page called 'liquid light', and put the rider on it that there's no practical experimental evidence for it. Dan100 15:35, Dec 22, 2004 (UTC)

Laser article not really the place to validate/vet childhood comic book laser fantasies

I removed the section

"Many assumptions are made when criticising an effect in a fictional, future, or alternate universe: Not all elements and conditions of the effect are given or known, and as follows it is unwise to apply one's limited knowledge and prejudices to what is seen as new, strange, or different. For example, most viewers are unaware of nonlinear and nonconservative physical processes: an intense beam increases its medium's refractive index, slowing itself down; a medium has resonant or absorptive peak wavelengths (or frequencies), causing a phase change to materialise from certain applied energies; an intense beam's EM fields polarise nearby materials, drawing them in—the mysterious beam with unknown boundary conditions on Earth would be influenced by the ubiquitous amounts of silicate and aluminate dust floating in the air, perhaps giving rise to ball lightning. Interstellar and intergalactic space are not even perfect vacua as beams have hydrogen, the microwave background, cosmic rays, dark matter, and virtual particles to interact with. In other words, if a particular influence is invisible, its collisions with other invisible or less-visible influences may give rise to visible influences which are hard to explain without knowing what they were. Criticism about known implementations of radiating systems is safer."

Why did I remove it? It's horrible. A small section on popular misconceptions of lasers does not at all need an overly pedantic, grasping and rediculous[sic] discussion of all the possible caveats which might allow the misconceptions to be true (ball lightning and ubiquitous silicate and aluminate? virtual particles? you're kidding right?)--Deglr6328 20:30, 21 Dec 2004 (UTC)

I never wrote anything to allow misconceptions to be true! It was an NPOV exposition of common and uncommon interferences to directed energy, which may or may not actually be a laser beam, which was in response to misconceptions surrounding a laser beam. If you want to make the article more relevant, fine, but you're showing the stupid behaviour that so many other "authoritative" editors have: not rewriting, making, or splitting articles, but deleting from them entirely when they are relevant and interesting. lysdexia 22:43, 21 Dec 2004 (UTC)

Not only is the paragraph NOT relevant or interesting, it's factually incorrect and a bit crankish too. Let's look at the line "an intense beam's EM fields polarise nearby materials, drawing them in—the mysterious beam with unknown boundary conditions on Earth would be influenced by the ubiquitous amounts of silicate and aluminate dust floating in the air, perhaps giving rise to ball lightning." I can't even tell what you're trying to say there and it looks like crazy rambling with some scientific words thrown in to lend an air of plausibility so far as I can see. Now let's take the sentence "Interstellar and intergalactic space are not even perfect vacua as beams have hydrogen, the microwave background, cosmic rays, dark matter, and virtual particles to interact with." Now, anyone who knows anything about lasers could spot this for the kookery that it is. Firstly the concentration of H in interstellar space is phenomenally low. Like, 2-3 atoms/m^3 low. Far below what is needed to make a beam visible. Second, cosmic rays are even fewer. Third, dark matter?!? We dont even know what it is let alone the intensity of a laser it would take to interact with it. Fourth, virtual particles are created and destroyed on the Plank scale; we have no lasers in existence which are powerful enough to be capable of forcing virtual particles out of the vacuum (this takes something like 10^28 W/cm^2 if I recall, an insanely high power). Now, if you think I'm showing "stupid behaviour that so many other 'authoritative' editors have" been removing the factually incorrect and ludicrous additions you've made to the article then I'm awfully sorry for that, but it's what should be done. Oh by the way, I work here, and while that sure doesn't automatically make me some all knowing laser guru, I do think I know a thing or two about them.--Deglr6328 22:44, 21 Dec 2004 (UTC)

Okay, bub, if you don't know what a sentence is trying to say, then have you tried using a question? It's when you put out your confusion in words so you can get rid of it. Your next complaint is again your missing the point of the misconceptions section, especially that of my additions which I already wrote to you earlier on this page. I wrote nothing about a light beam scattering off space debris to become visible solely; I wrote nothing about a light or laser beam having to hit such debris to become visible. Reread that sentence. It was about a so-called vacuum for laser beams, and it was about so-called laser beams. What does it take to know anything about dark matter or anything else in space? Based on how larger systems behave against known gravitic and inertial forces, the concentration of dark matter is projected to increase from the stellar to the extragalactic scale. Are you forgetting what section you're talking about? It was about supposed lasers in the media. You haven't yet made an argument against talking about anything related to lasers, media included, and that is what a general article about lasers should have. lysdexia 23:47, 21 Dec 2004 (UTC)

That paragraph is pretty much nonsense. Has no place on wikipedia. Dan100 15:39, Dec 22, 2004 (UTC)

I know much about lasers and optics, and I fully agree with that. RPaschotta 16:14, 25 Dec 2004 (UTC)

I've been busy with other things than Wikipedia but I fully support Deglr6328 and I think that the contributions by Lysdexia have no place here since they do not represent common consensus in the field. The "article needs work" tag is not necessary in this version. Han-Kwang (talk) 21:12, 25 Dec 2004 (UTC) (Ph.D. in laser spectroscopy and nonlinear optics)

Support and elaborate on your accusations. Common consensus was never a prerequisite for articles' content. It's not nonsense, and it's self-explanatory. The material was important and relevant to popular misconceptions, and removing it is like neutering the article. He left my clause about criticisms of depictions in the media, yet there isn't an explanation any more. I made many contributions to the article which were kept or edited, which were against the knowledge of laser experts throughout this talk page and which could not be argued against. And here, there are no arguments to support removing the rest. Ye are merely making stuff up. I'll put the attention tag back up. lysdexia 03:39, 29 Dec 2004 (UTC)

Discussing with you is like explaining to a 4-year old why an orange is not a pear. I am not going to waste my time with that. Han-Kwang (talk) 20:50, 31 Dec 2004 (UTC)

It doesn't even read like original research -- more like original speculation by someone with a strong grasp of scientific buzzwords. --Carnildo 01:27, 5 Jan 2005 (UTC)

Laser applications

Laser applications needs a lot of work. It currently has three small sections on the normal applications of lasers, and a bunch of sections on the military uses of lasers. The average reader is much more likely to come into contact with a laser when it's used to scan their groceries than on the receiving end of a Death ray, and it would be good for the article to reflect that. The scientific section only lists four applications. —Ben Brockert (42) UE News 22:24, Jan 2, 2005 (UTC)

3 or 4 quantum levels

From article:

...those which involve three or four energy levels rather than two make better lasers because the electrons are kept above the ground state...

The given reason for using 3 or 4 quantum level systems for lasers does not agree with my understanding of the physics. AFAIK, the idea is that lasing occurs when there is population inversion (of electrons) between two energy levels whose separation is equal to the energy of one photon of the light in question. If you only have 2 levels, then when a photon is emitted, an electron is moved from the higher level to the lower level, which reduced the population inversion. With 3 levels, the lower level can itself then decay quickly to the ground state below, which removed population from the level at the bottom of the optical-wavelength gap. Reducing the population in the lower level increses the populatino inversion, increasing the gain of the lasing material. Having electrons in the ground state is not itself a problem, unless the ground state is also the lower state of the optical-transition involving in lasing, in which cases population in the lower (ground) state reduced the population inversion and thus reduces the gain. Having more electrons in the ground state is actually good in some cases, as it makes pumping more effective, wheras having all the population in a relatively stable upper level that did not increase population inversion would be bad, if the pumping did not promote electrons from that level.

I fully concur. Go ahead and change it. (ps. sign your edits plz. :o)--Deglr6328 21:32, 18 Mar 2005 (UTC)

coherent/incoherent

I'm going to do something about "coherence," particularly the diagrams. But first a nitpicker question. Suppose we sequentially reflect some laser light from several frosted screens. Should we call the resulting wave "coherent?" After all, the phase difference between any two sampled points in the wave is not changing with time. But the wave itself is a mess, and doesn't really fall under the description of "coherent light" that most people use. Does that make it incoherent, or is there a more appropriate term? --Wjbeaty 02:10, Mar 23, 2005 (UTC)

I think the diagrams there are quite lovely actually. What is wrong with them exactly?--Deglr6328 05:57, 23 Mar 2005 (UTC)

The object of a diagram is to educate, not decorate. I'd rather have a non-lovely diagram which gives me insights into the physics.

Back in school, when I finally understood the nature of spatial/temporal laser coherence, I realized that my original misunderstandings had mostly been caused by these exact diagrams, and they misled me because they purport to explain coherence, but instead they only explained phase difference.

Also, neither light waves nor water waves look anything like these transverse waves on strings. The "parallel pieces of string" concept leads us away from understanding coherence, so the diagrams form a learning barrier, not a learning aid.

To explain coherence, the waves in the diagram must superpose, rather than existing on separate pieces of string, i.e. they must all be added together to become one single wave on one single string.

Now the real question is: can I come up with a "coherence" diagram without resorting to mpeg movies.--Wjbeaty 23:52, Mar 23, 2005 (UTC)

It's called "abstraction".--Deglr6328 00:52, 24 Mar 2005 (UTC)

Rinky-dink

Okay, I've mildly tinkered with part of one section of the article, whilst also reading this bit about lasers [3] on Greg Goebel's wonderful site. With regards to the cliche about cat burglars spraying mist in the path of 'security lasers' - and I assume the writer was thinking about the tightly-clad buttocks of Catherine Zeta Jones, in her 1999 film "Entrapment" - I believe this gag was first used in one of the early Pink Panther films, specifically the 1963 original. However, I'm not sure if it wasn't the 1975 "The Return of the Pink Panther" or the 1976 "The Pink Panther Strikes Back". It's only a short, juvenile trivia point, which I would enter as a dashed aside - like this - but it would be nice to be sure. Short of spending a week downloading the films with Emule or paying money to rent the films, something which I am not prepared to do, I have no way to verify this for definite, i.e. to see it with my own eyes. I pass the torch on, to you. Yes, you.-Ashley Pomeroy

Great picture, by the way; nothing says science more than earnest-looking young men wearing goggles whilst staring at frickin' laser beams. They're so Devo!-Ashley Pomeroy 11:54, 6 Apr 2005 (UTC)

Laser Classification Reference

For anyone that would like to revise/improve the laser classifications, here's the source with some comments:

Excerpts from the Center for Devices and Radiological Health (CDRH) regulation 21 CFR 1040.10 and 21 CFR 1040.11, verbatim, comments italicized: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?FR=1040.10

TITLE 21--FOOD AND DRUGS

CHAPTER I--FOOD AND DRUG ADMINISTRATION

DEPARTMENT OF HEALTH AND HUMAN SERVICES

SUBCHAPTER J - RADIOLOGICAL HEALTH

Sec. 1040.10 Laser products.

[...]

(What the parameters k1 and k2 are for any wavelength) (What k1, k2 are for selected wavelengths)

(5) Class I laser product means any laser product that does not permit access during the operation to levels of laser radiation in excess of the accessible emission limits contained in table I of paragraph (d) of this section. (4 wavelength ranges spanning 180nm-1000um, divided up into exposure durations, then limited based on radient energy, power, exposure, radiance, or integrated radience)

1 Class I levels of laser radiation are not considered to be hazardous.

(6) Class IIa laser product means any laser product that permits human access during operation to levels of visible laser radiation in excess of the accessible emission limits contained in table I, but does not permit human access during operation to levels of laser radiation in excess of the accessible emission limits contained in table II-A of paragraph (d) of this section. more-or-less says: all the same as class I, except visible (400-710nm), where the emission limits are 3.9 uW (over >1000 s)

2 Class IIa levels of laser radiation are not considered to be hazardous if viewed for any period of time less than or equal to 1×10 3 seconds but are considered to be a chronic viewing hazard for any period of time greater than 1×10 3 seconds.

(7) Class II laser product means any laser product that permits human access during operation to levels of visible laser radiation in excess of the accessible emission limits contained in table II-A, but does not permit human access during operation to levels of laser radiation in excess of the accessible emission limits contained in table II of paragraph (d) of this section. more-or-less says: all the same as class I, except visible (400-710nm), where the emission limits are 1.0 mW (over >250 ms)

3 Class II levels of laser radiation are considered to be a chronic viewing hazard.

(8) Class IIIa laser product means any laser product that permits human access during operation to levels of visible laser radiation in excess of the accessible emission limits contained in table II, but does not permit human access during operation to levels of laser radiation in excess of the accessible emission limits contained in table III-A of paragraph (d) of this section. more-or-less says: all the same as class I, except visible (400-710nm), where the emission limits are 5.0 mW (over >3.8 × 10⁻⁴ s)

4 Class IIIa levels of laser radiation are considered to be, depending upon the irradiance, either an acute intrabeam viewing hazard or chronic viewing hazard, and an acute viewing hazard if viewed directly with optical instruments.

(9) Class IIIb laser product means any laser product that permits human access during operation to levels of laser radiation in excess of the accessible emission limits of table III-A, but does not permit human access during operation to levels of laser radiation in excess of the accessible emission limits contained in table III-B of paragraph (d) of this section. lots-o-parameters, but says for >400nm, 500mW is the limit; 315-400nm, 495mW limit; 302.4-315nm, 1.5mW × 10^{(λ−302.4)/5} limit; 180-302.4nm, 1.5mW limit

5 Class IIIb levels of laser radiation are considered to be an acute hazard to the skin and eyes from direct radiation. e.g. w/o collimating optics like IIIa

(10) Class III laser product means any Class IIIa or Class IIIb laser product.

(11) Class IV laser product means any laser that permits human access during operation to levels of laser radiation in excess of the accessible emission limits contained in table III-B of paragraph (d) of this section. anything beyond a IIIb

6 Class IV levels of laser radiation are considered to be an acute hazard to the skin and eyes from direct and scattered radiation.

Prometheus235 15:16, 31 May 2005 (UTC)

Lasers are masers

Hello. So I believe there is a problem with this article. Namely, the discussion of what a maser is has become anachronistic, and misleading, and thus the way it is presented in this article is, well ... wrong. The issue is a bit tangled. So, as is stated, lasers were first derived from the developement and conceptual framework of the maser, where a maser was essentially the same type of device but restricted to the microwave region of the spectrum. However, this is an old definition it seems. It doesn't require much research to confirm this claim. There are now a large number of "masers" that have been developed which operate all around the rf spectrum, even near the bottom of the VLF. These are very clearly not "mircrowave devices." This is because a maser is generally meant to stand for molecular amplification by stimulated emission of rediation.

Now, this is extremely important for a number of reasons. The first being far too many "experts" who work with lasers are completely ignorant of the fact that these types of devices exist for a large array of spectral frequencies, and that each has very unique, interesting, and important features (I can give details if you like). In fact stimulated emission can and has been extended to fairly exotic settign. Second, if one wants to extend the defintion of a laser to include these devices, then one needs to explain that when one refers to "light" one is really thinking of "light" as a any type of photon emission; which is not usually the case, and thus a bit of a non sequitur. Third, though this article is quite nice in some ways, and provides a decent background in an engineering sense, its theoretical part is quite absent. Though it s true that laser is a device, it is also true that a dishrag is a device. The word device carries no inherent laser-ness. It is a wasted noun. On the other hand, a laser is a maser, which is also a device, and is a word that carries details related to the actual underlying properties of system, plus leading, in an expansive way, to the more theortic issues at hand. When I say recent advances in maser research, the word recent is used euphamistically. In fact, masers have been around in this permuation of there meaning for at least a decade. Anyway, parts of this page need to be rewritten in order to get this up to date with the current science. 66.143.168.143 20:47, 16 July 2005 (UTC)

You've still cited no source which corroborates the (nonsense) claim that "a laser is a maser". MASERS work in the GHz spectrum and below and lasers operate in the UV, visible and IR spectrums. That's it. The fact that stimulated emission has been extended to exotic regimes in no way validates the claim that lasers are some kind of subset of masers. There are X-ray lasers now in existance as well, would you claim that lasers are actually a subset of masers? No one conventionally defines them that way [4]. If, as it seems you do, fancy yourself such an expert above the experts you'll have to provide a much better argument than you have here for the changes you want to make to the fundamentally accepted definition of a laser. I might also remind you that wikipedia is also not a place for original research or the changing of widely accepted definitions to suit an editors whim or suspicion. --Deglr6328 21:01, 16 July 2005 (UTC)

Frankly I'm shocked. Anyway, I appreciate your concern for rewriting conventional definitions. Luckily, that is not what I am proposing, but rather to get the current one into the 20th century :) (maybe the late 20th century ;-)). So, the term maser, as refered above and on the link, was given by the Nobel prize winning physicisat at least as early as 1964 (please see the links at the maser article). That being the case, then the answer to your confusing question is mostly yes. A xaser is a maser, a laser is a maser, a raser is a maser, and a maser is a maser. If you wish, an optical laser is a maser, an x-ray laser is a maser, a radio-laser is a maser, and a microwave laser is a maser. This is confusing though, since light almost always conventionally refers to the optical spectrum. So, there's that. A xaser is not a laser though, since they operate at totally different frequencies.

Now, the link to the photonics dictionary is not at issue. That definition is accurate up to the level at which it defines itself (in other words, it does not pressume to subsume the definition of a maser or an x-ray laser in that article. I am refering to the article here at wikipedia.

Now, since atoms are molecules, our confusion ablates once we start looking at the way in which stimulated emission actually works in these systems. The Zeeman exchange maser is a good example of a maser which does not have to operate in the microwave frequency range at all. For background and info, see:

1. T.E. Chupp, R.J.Hoare, R.L. Walsworth, and Bo Wu, Spin-Exchange-Pumped He and Xe Zeeman Masers, Physical Review Letters, 72 (1994) 2363-2366

2. C.V Rice, and D. Raftery, Rubidium–xenon spin exchange and relaxation rates measured at high pressure and high magnetic field, Journal of Chemical Physics, 117 (2002) 5632-5641

3. M.G. Richards, B.P. Cowan, M.F. Secca, and K. Machin, The He nuclear Zeeman maser, Journal of Physics B: Atomic, Molecular, and Optical Physics, 21 (1988) 665-681

There are hundreds more (actually thousands). You might save me the time by going to web-of-science and doing a couple searches on your own. It is true that some people say x-ray laser, some say xaser, and some say, more generally maser. That is why we so desperately need to clarify the terminology, so people can read the literature without being more confused. 66.143.168.143 22:02, 16 July 2005 (UTC)

Btw Deglr6328, the term raser is used in the literature (and could use a wikipedia entry btw) - in reference to your comment on the maser page. It does not get alot of use in titles, but occasionally it does, and it has made it into the body of many texts on related topics:

1. Bosiger, P.; Brun, E.; Meier, D., Instabilities and phase changes of the first order of the ruby raser, Helvetica Physica Acta, vol.52, no.3, 25 Jan. 1980. p. 375

2. Yu. M. Seidov, É. M. Shakhverdiev, and I. I. Abbasov, Condition for generation of radiation in rasers, TECHNICAL PHYSICS 42 (10): 1238-1238 OCT 1997

66.143.168.143 23:11, 16 July 2005 (UTC)

No, and now I strongly suspect that you are trying to insert nonsense into the article merely to see if you can. With GROSSLY scientifically inaccurate statements like "Now, since atoms are molecules..." and "A xaser is a maser, a laser is a maser, a raser is a maser, and a maser is a maser." then later "A xaser is not a laser though, since they operate at totally different frequencies.", I just don't know what to say. I mean what do you think "xasers" and masers operate at? The same frequency? Virtually no one uses "xaser" and no one EVER uses maser to describe x-ray lasers. Your statements are rife with incomprehensible gibberish and frankly I don't know what your citations are supposed to prove at all. Zeeman masers are zeeman masers. That's it. So what. Also the sentence that you keep inserting in the maser article:

"maser...acronym has been appended in the current usage, and is usually taken to stand for "molecular amplification by stimulated emission of radiation" [1]. Under this defintion, an optical laser is a specific type of the more general maser"

is just wrong. This usage gets ~20 hits on google [5] (most of which are merely repeats of a what seems to be a widely distributed, originally french, acronym list and the rest seem to be mostly mentioned on openly posted physics forums or science fiction novels) it gets precisely NO hits on a scitation search. I doubt anything of much value can be gained from continuing this conversation. Please stop adding nonsense to wikipedia. It is not the job of wikipedia to redefine terms. It is insanely frustrating to have to constantly spend time arguing with anonymous editors who insist on inserting incorrect information on wiki. --Deglr6328 23:38, 16 July 2005 (UTC)

Deglr6328, have you lost your mind :). Yes indeed, what is a Zeeman maser. Can we please be civil btw, I am no newbie to wiki or to science, and it is unlikely you can disuade me with your blatherskism.

So first, yes, an atom is a molecule by the definiton given, of all places, here. Though often we talk of bound states here in my chemistry and physics departments, the issue right now is one of conistency with definitions (that is, the defintion of the maser in particular). Geez, must I explain such an elementary concept? So we have molecular gases, then we have monatomic gases, etc ... so which would a noble gas be? (common usage, wikipedia definition, etc.). Look into it, you might be surprised (google could work as well). Let me provide a bit more explanation for the uninformed. In statistical kinetics (generally physical chemistry that is), for example, we often deal with ensembles of atoms, wherein we deal with things called molecular collisions. This is pretty basic, and you may argue confusing, that kineticists use the term molecule to refer to atoms in atomic gases. Nonetheless, nobody apparently asked for your permission, since that's the way it's been done for decades now. So that's cleared up.

Now let me explain what a maser is one more time. A maser is any amplifier that produces coherent electromagnetic waves due to stimulated emission. In current usage it stands for molecular amplification by stimulated emission of radiation. Notice the word molecular. Is it coming together now? The reason I reference the Zeeman maser is because, for example, in the reference above, if you considered actually reading it, you would have noticed that one of the coupled Zeeman masers operates at 3510 Hz (can you guess which one? -- you could always read it). Is that in the microwave range? If you answered no then we're getting somewhere. As far as xasers are concerned, you're not wrong. It seems to be standard in the x-ray laser community to refer to x-ray lasers as x-ray lasers. Which is fine. Does that mean that an x-ray laser is not an amplifier that produces coherent electromagnetic waves due to stimulated emission? -- no. So what is your point? If your point is you haven' ever used this term, then, as shown with raser and molecule, the answers has to be, so what?

And what do mean by 20 hits? What is that based on? What are your search terms and what is your search engine? I can give you mine if you like.

Anyway, If someone else would like to step in I would be much obliged. I have read many articles on these subjects, and all that I am interested in doing is clarifying the language, not getting into a 10 year olds flame war. If you need more references, I guess I can provide them. If you would like me to explain any of the mathematics or physics in any of the references I've already given, I suppose I can teach you that (though if I have to, then why are you arguing with me?). If you need other examples of masers that are not microwave, I can do that. What I can't do is sit here while you present no facts, provide no citations, and demonstrate no coherent argument at all as to why I am wrong (other than pointing out your confusion on varying related levels of science); and doing so in a rude and obnoxious way. I mean, how many times must you be wrong before you take on a more humble attitude? You were wrong when you said rasers are in theGHz range, your were wrong when you said "term raser is nonexistant in the literature," your were wrong when you said and atom is not a molecule, and you were demonstrating you inability to reason when you said "Your statements are rife with incomprehensible gibberish and frankly I don't know what your citations are supposed to prove at all;" as that would have been clear had you spent any time reading them at all. So, in the name of this discussion, why don't we just accept that maybe you know some things, and maybe I know some things, and together we might be able to straighten this out. Deal? 66.143.168.143 00:43, 17 July 2005 (UTC)

If you are trying to claim that because the term maser can be applied to VHF emitting devices (zeeman masers) then the term can also be likewise applied to lasers and "xasers" you are wrong. The term is not conventionally used this way. While the term "raser" might not be nonexistant and I was technically wrong there, it IS *virtually* nonexistant in the literature (do a scitation search, there is precisely ONE relevant paper ever published with the term). And I never said Rasers are in the GHz range. I said Masers are considered to be in the GHz and below region. Furthermore, to say that "individual atoms are also called molecules" is to stretch and confuse a definition so incredibly thinly as to be laughable. You seem to be bent on using the most arcane and torturous definitions of terms possible to suit your needs. Ironic since you claim to merely want to 'make things clearer for the reader'. Your citations of Zeeman masers no more proves that lasers are masers than it proves xasers are masers. This is really absurd. Anyway, whatever, like I said I'm done here, there is enough conversation above to allow other editors to see the situation make any appropriate future edits. --Deglr6328 01:13, 17 July 2005 (UTC)

Okay. Bye then.

Let me add a couple parting words to any spectators who are present. The first, for those of you who don't know, Scitation articles really only go back to ~1996. This being the case, what Deglr6328 said is true, there is only one citation for raser in this search engine. However, if one uses, for example, web of science, one gets about 10 more. Now, this still seems like not very many, and it isn't. However, this only represents titles and abstracts with raser in it, not full scale texts which may mention rasers. This is why the term, which is fairly well-established as an alternative termoinology, is not used very often. It is certainly fair to say it is rarely used, or even that it is resisted by the scientific community for whatever reason. As a matter of fact, I would recommend against using it unless you really know what you're doing.

With regards to the defintion of a molecule, I must admit to having been a bit confused myself at first by this. When I first saw the acronym for maser expanded as "molecular" I thought of covalently bonded (or bound state) phenomena, and thought the defintion was that much more confusing. But as I thought it over, and dug a bit deeper, I found that using the kinetic definition is actually extremely natural. For example, in a spin-exchange maser, the spins are exchanged due to atomic collisions, which leads to the coherent state of the system. Thus, in the terminology of collisional kinetics, a molecule is just the base element. I do however agree that this can be confusing initially. I hope that makes it clearer.

Finally, the basic confusion has been obfuscated I think by alot of nonsense, so let me restate it as clearly as I can. The word maser is most often taken to be an acronym for "microwave"-aser. However, it is basically standard to refer to what may be termed rasers as also being masers. That is stimulated emission in the radio frequency range of the spectrum. Thus, one of two things must be true. One, that the traditional acronym for maser is false, in that a maser is not a microwave-aser. Or two, the acronym is correct and rasers are not masers. If one looks at the literature, they will quickly see that the second option must be patently false, as there is simply too much literature on masers that emit in the radio frequency range, such as the ones mentions above in the references. Thus, one must consider that the acronym "microwave-aser" is somehow wrong or misleading. Along these lines, many have been led to a similar conclusion. Most notably, Charles H. Townes, the noble prize winning physicist in maser and laser research, presented no later than 1964 the appended acronym for maser that is "molecular amplification by stimulated emission of radiation." A quote from Townes in 1964, that is referenced here [6] , goes "The idea [of stimulated emission] has been successfully extended to such a variety of devices and frequencies that it is probably well to generalize the name - perhaps to mean molecular amplification by stimulated emission of radiation."

Now, the problem is, as is always the problem, this ruffles feathers in people who prefer the incompressible contradiction that they are used to, rather than a scientifically rigorous definition that makes some sense. So, if we define maser as "microwave-aser," then many of the masers in existence today are, by definition, not masers. However, if we use Townes' generalization, then these modern masers are masers, but unfortunately, then lasers, xasers, etc. are also masers, as the definitions subsumes those at this point by thinking of molecular-aser in the kinetic sense. This is very frustrating to people apparently. The point is, this mess is not "my" mess, this is a mess generated by alot of other people, but must be made sense of. Whatever is ultimately most preferable to the wikipedia community is fine with me; but many, not just me, and not just Deglr6328, have been confused by this, and so it must be mentioned when one is going to mention masers at all in an article. And insults and threats of illegitimacy are irrelevent, this is the state of things which I think can be confirmed when one looks into it a bit. What we need is an explanation, because though a defintion on wikipedia is not meant to "change" or redefine scientific terminology, it is meant to reflect the state of the field in question. And so, since the state of the field is confusion, we have the option of either presenting that confusion in the state it exists in in its entirety, or provide some direction by which people can find their way therough the labyrinth on their own and arrive at the correct conclusions. What is currently presented in this article does neither. If nobody feels qualified to make the necessary changes, or iof they are having truble understanding the nature of the issue, then I can do it easily. However, in an attempt to observe the community spirit of wiki, I would like to ask if anybody has any other comments before I do so. 66.143.168.143 05:13, 17 July 2005 (UTC)

"Most notably, Charles H. Townes, the noble prize winning physicist in maser and laser research, presented no later than 1964 the appended acronym for maser that is "molecular amplification by stimulated emission of radiation."

Who uses this term?! nearly nobody [7] exept you! It gasped its last mere seconds after it was suggested by Townes just like graser and UVaser and countless other suggested scientific terms. If we want to avoid confusion for the reader, the first thing we should be doing is NOT basing our explanations here on dead/invented/unknown/unaccepted/totally disused definitions. Its pointless. That is all. bye.--Deglr6328 05:59, 17 July 2005 (UTC)

Geez Deglr6328, why such desperation? The world will go on. Consider this. The terminology of the laser could be equally confusing, as light 'usually' refers to the visible spectrum. However, with the popularity of the term laser, the term light in the acronym has been extended to mean really any energy of photon. So an xray laser, an ir laser, a uv laser, etc., all operate with photons, so we can make sense of the terminology, and think of them all as lasers. However, with a maser we have "microwave" to deal with. It seems impossible to extend the meaning of microwave to radio frequency, etc. One perhaps could have wished that maser hadn't caught on, and that people refered to microwave-asers as microwave lasers, and rasers as rf-lasers, and thus the issue would never have been important. But, unfortunately this has not been the case. Instead, stupid people like me, spend several days of their lives trying to understand how in the world a maser could emit in the VLF. Since the answer is staring us in the face, namely the appended acronym above, the only reasonable conclusion is that everyone who uses maser to refer to rf-lasers is implicitly taking as an acronym "molecular-aser;" as otherwise they would be making inconsistent statements. In fact, this seems to be the case when you talk to these people. Maser seems to be the more general term. But even if it weren't, don't you think it is the role of places like wikipedia to clarify these types of issues for the general public, as really this is just a semantic issue having to due with common usage of basic terminology? Perhaps there is a way of presenting this that would be less upsetting to you? 66.143.168.143 06:56, 17 July 2005 (UTC)

Hi, just to clarify something, I'm an optics student and we have always been taught that Maser refers to the original official definition, "molecular amplification by stimulated emission of radiation". I hadn't come across maser referring to microwave wavelength lasers before, and possibly this is the same for all students new to the subject, and so is possibly a definition not used at all anymore?

As a counter-example, as a Ph.D. student in optoelectronics a few years ago, I never heard of the term "maser" meaning anything but "microwave amplification by stimulated emission of radiation". Looking into it further (e.g. from the discussion here, and from Jeff Hecht's book Beam), it looks like the term "optical maser" is/was mostly used by those who wish to emphasize Schawlow and Townes' and Bell Labs' (substantial and very important) contributions to the field. Notable among those who have chosen to emphasize these contributions are Bell Labs and Townes himself. I have tried to more or less obliquely refer to this situation in the text, and I included a link to Bell Labs' web page describing the history of the laser, written in 1998, showing that by that time even Bell Labs had begun using the term "laser". As for what is the correct expansion of the acronym "maser", that is a question for the Maser article, not the laser article.

PS It is helpful to sign your contributions to Talk pages using "~~~~" if you have an account, or otherwise by some name you want the rest of us to think of you as.

-- The Photon 01:05, 5 December 2005 (UTC)

I second the opinion of The Photon. --danh 18:00, 5 December 2005 (UTC)

Has anyone made a LASER weapon

If you have made one please tell me how you made it(I already know how to make one). Dudtz 8/19/05 6:51 PM EST

Image:Laser spectral lines.png

http://en.wikipedia.org/wiki/Image:Laser_spectral_lines.png

I found this picture misleading:

no uniformity in the font usage: Nd:YAG vs HO:YAG (is it holmium and oxygen doped YAG? )
RAMAN lines vs Ramen shifted
El:YAG >>> should be Er:YAG
Nd:YAG/Glass and Nd:YAG & Nd:Glass

Where is the He-Ne laser lines? (at least ~633 nm) Where is the UV representitives (excimer lasers)?

Can you fix it or make a new one?--Deglr6328 04:06, 26 August 2005 (UTC)

I need a video

Can anyone give me an url where I can get a video about how works a cd-reader (the pick up part)? I need it for a school work about lasers

Darío Lescano - dariofl@latinmail.com

Gordon or Gould coined terms and gained patents?

In the history section, the article states

Gordon also coined the word iraser, intending "aser" as the suffix and the spectra of light emitted at as the prefix (examples: X-ray laser = xaser, UltraViolet laser = uvaser) but these terms never became popular. Gordon was also credited with lucrative patent rights for a gas-discharge laser in 1987, following a protracted 30 year legal battle.

It is not clear whether "Gordon" refers to Townes' collaborator J.P. Gordon, or to the coiner of the term laser, Gordon Gould. According to recent obituaries, Gould was the one who received critical patents for the laser. The Photon 06:24, 30 September 2005 (UTC)

Formatting of the page

after recent edits, is now quite horrid in IE..... --Deglr6328 07:24, 5 October 2005 (UTC)

Apologies. I am not editting with IE. I'll do what I can to avoid images stacking up, and check it out in IE from work tomorrow.The Photon 03:58, 6 October 2005 (UTC)

Looks good now.--Deglr6328 05:18, 13 October 2005 (UTC)

History events that might be included

These are some historical developments that greatly overshadow the "recent innovations" included in the article, but I don't know enough about them to write them in to the article. I see several items creeping in that might be better off in Laser applications, but at least one or two of them are probably appropriate here as well. Please add to the list. The Photon 15:54, 11 October 2005 (UTC)

Invention of C02 laser.
Invention of optical fiber laser (gain medium doped into glass)
Introduction of first commercially available laser.
Invention of dye laser.
Invention of the hologram (first gee-whiz use of lasers for the general public).
Introduction of first successfully commercialized industrial laser.
Introduction of first lasers visible to general population: supermarket scanner?
Introduction of first consumer device with laser: laserdisk?
Introduction of first mass-market consumer device with lasers: CD player.

CO2 laser in 1964, dye laser in 1966, Nd:fibre laser in 1961, EDFA in 1987. Holography was actually invented before the laser, in 1948. Not sure about commercial availability, etc. -- Bob Mellish 16:28, 11 October 2005 (UTC)

Rival Claimants to the Invention of the Laser other than Townes, Gould, Maiman

A somewhat speculative paper by Myers and Dixon cites the following two fellows as rival principal inventors of the laser. Nicolaas Bloembergen (three-level MASER) with U.S. Patent No. 2,909,654 (filed October 15, 1956); Robert Dicke with U.S. Patent No. 2,851,652 (filed May 21, 1956). From a IEEE paper (pub. date unknown, cited by Karl Jorda in Commentary, "The Thirty-Year Laser Patent War", IDEA, Vol. 43, No. 3, p. 545) "Who Invented the Laser?" by Robert A. Myers and Richard W. Dixon. Bloembergen is a Nobel laureate, and according to anecdotal evidence apparently erroneously did not think his invention applied to optical radiation (but presumeably, according to the paper authors, it does).

To cite natural forces as an "invention", the atmosphere of Mars essentially amplifies sunlight and acts as a sort of natural laser. This was brought up as a defense during the Gould litigation to try and defeat one of Gordon Gould's patents.

Definition again

"(A laser is) an optical source that emits photons in a narrow, polarized, coherent beam of near-monochromatic light, consisting of a single wavelength or hue."

Therefore, most semiconductor lasers aren't lasers, because they don't emit particularly narrow beams. (Nor always lase in a single polarization The Photon)
Therefore, many Nd:YAG lasers aren't lasers because they're often unpolarized.
Therefore, a modelocked Ti:sapphire laser isn't a laser because it's far from monochromatic.

Recent edits are narrowing the definition of laser down too much, again. Please be careful about being to specific when it comes to the definition. --Bob Mellish 01:39, 13 October 2005 (UTC)

Why not fix it then?--Deglr6328 05:20, 13 October 2005 (UTC)

Proposal: "A laser is an optical source that produces light from an oscillating optical cavity, using stimulated emission as the gain mechanism. The output is highly coherent in comparison with classical artificial sources, and in many cases can be designed to be polarized and/or near-monochromatic. These features make lasers important because ... [gotta work on this part]" --- I would prefer to make the first sentence less technical---any ideas? Do we need to say "light or other electromagnetic radiation" to include x-ray lasers, etc? --The Photon 16:15, 13 October 2005 (UTC)

No need for the "These features make lasers important because" section as this is already present in the "uses" section.--Deglr6328 16:40, 13 October 2005 (UTC)

I'm more thinking of the "encyclopedic" style. (My opinion only) the first paragraph "ought" to summarize the importance of the whole article in as few sentences as possible. The whole article "ought" to explain to general readers (not physicists) why lasers are important to them. Some more subtle phrasing would be better than "X is important because".--The Photon 01:32, 18 October 2005 (UTC)

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