Talk:Laser/Archive 1

message: 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)
thread_title: Laser safety

message: 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)
thread_title:  Removed parts 

message: "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)
replies: text:  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)
thread_title:  Mist 

message: 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.  "
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)
replies: text: 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)

text: 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)
replies: text: 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)
replies: text: 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)
replies: text: 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)

text: 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)

text: 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)
replies: text: 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)
replies: text: 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)
thread_title: Sorry but don't like this "liquid light" stuff