User talk:Withead

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Hello, Withead, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are some pages that you might find helpful:

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I hope you enjoy editing here and being a Wikipedian! Please sign your messages on discussion pages using four tildes (~~~~); this will automatically insert your username and the date. If you need help, check out Wikipedia:Questions, ask me on my talk page, or ask your question on this page and then place {{helpme}} before the question. Again, welcome! Wizard191 (talk) 17:50, 13 October 2010 (UTC)[reply]

Hello Wizard191, Yes, I do need help. But I don't understand many of the "How To.." articles. They assume more computer literacy than I have at the moment. My grand-daughter is trying to help... My expertise is in Helium Neon gas lasers dating back to 1961 Thanks, Withead

He-Ne wavelength[edit]

Hi, You might have seen that I added a tag to your change, but you probably know what you're talking about. So don't bother with a reference but I just wanted to know: Are you sure about those being red (not IR) lasers in the RLG's? I had thought they were 1.15 (I think these are easier to be made single mode, for instance, don't have to be as short). I had just written that based on my memory, but might have been mistaken. Thanks, Interferometrist (talk) 22:01, 7 May 2011 (UTC)[reply]

Hello again, and thank you VERY much for your informative and interesting reply! I'm pressed for time but wanted to get back to you about the things you mentioned. First, thank you very much for the reference on ring laser gyros which I intend to read in more detail when I have a chance. I guess I was wrong about the wavelength as you point out, and had just jotted that down from memory (my memory is far from perfect) so I removed the tag (and no, it doesn't really need to be cited in that article). More importantly, the reference you gave me WILL be added as a reference to the article on the laser gyro, and more importantly, might help me improve that article (again, when I have the chance).

More interestingly, when asking about the visible He Ne laser I was surprised (to say the least) to get a reply from one of its inventors! At first I was confused since I was familiar with the invention by Ali Javan but then went ahead and looked up the patents where indeed I saw yours as being the one for the He Ne laser oscillating at the familiar 633 VISIBLE line (as 99% of them are) but didn't get the same level of attention as an invention. (Which is funny, because the invention of the first visible laser got MUCH more mainstream attention than the earlier invention of the maser). Anyway that was of particular interest to me because a significant amount of my work has been using He Ne lasers. At one time I practically equated "laser" with He Ne, until laser pointers using semiconductor lasers became commonplace. But although the spatial characteristics and general appearance of their beams are similar, the He Ne is really one of the very most temporally coherent and frequency-stable lasers which is essential to some of my work. And for many years it was the only laser I ever saw, or certainly the only one they would even let me get my hands on. And is still the one I depend on for its temporal coherence.

In fact I sort of chuckled when I saw the drawing in the patent since it resembled the very setup I have on my workbench with a He Ne tube having one internal mirror but a brewster window on the other side and an external front mirror (mounted on a piezo translator for frequency control). In between is a diaphragm like in your drawing for spatial mode control (the tube is wide enough for multi-mode operation, though not as wide as the 6mm of the one you used) where I was going to put an adjustable iris. I couldn't find an iris small enough so instead made a turret of pinholes which can reduce it to single mode (as I normally desire), just as you did (also using the wires).

Thank you also for the reference to the IEEE history page which I hadn't seen before. Searching it I found an interesting oral history of Charles Townes, and finally did locate your contribution which I shall read as well. As you can tell, the history of the laser and the He Ne in particular are of quite some interest to me, as I have and continue to be very involved with that particular device and its very fine properties. Best wishes, - Interferometrist (talk) 17:13, 10 May 2011 (UTC)[reply]

Hi. I did look at the history in a couple of the Wikipedia articles, and it is indeed unbalanced and a bit haphazard in its focus. But listen, rather than you spending time editing it and opening questions as to conflict of interests it would be better if you left that to others. I don't have much time myself for the next few weeks, but if you have any additional resources or personal information to supply in that regard (beyond the valuable IEEE site you pointed me to), you could best email me directly (and do include web links where available, or identification of material I could find in a university library). Use this link: [1]. I will also (and probably sooner) update the portion of the HeNe laser article on applications which doesn't properly reflect the broad range of uses that it had, particularly before semiconductor lasers had matured. I was going to mention the earlier bar-code scanners, laser printers, and optical interferometric testing, but please mention any others you can think of. Cheers, -- Interferometrist (talk) 12:55, 11 May 2011 (UTC)[reply]

Hello Interferometrist, I agree that the entries about the HeNe laser history should be probably be written by others, but I feel it is important to get facts and circumstances as close to what actually took place as possible. From this point of view, the History section is misleading. Of course, visible continuous lasers were recognized very early on as devices that would be very useful to have. But in the early sixties no one knew how to make one. There was no conception, beyond the pulsed ruby, how such a device could be made. ( I spent several months working on a arc lamp project to make the ruby go continuously). The problem was finding the gain medium that would amplify in the visible on a continuous rather than a pulsed basis. That was the crux of the matter; it wasn't a case of having several media to choose from based on engineering criteria. Very simply, there were nothing to choose from. In those early days the emphasis was almost entirely on discovering new and useful amplifying media. There are dozens of aborted experiments on materials that were never successfully inverted. Aborted experiments of course are not published. This is why the red HeNe was a breakthrough AT THE TIME. Nowadays of course, it is just one among many continuous visible lasers. This emphasis is lacking in the history section, to my mind. It is no big deal to look retrospectively at early efforts and wonder why early workers didn't see what is now so obvious. Editing Wikipedia articles is not a familiar experience for me; I do not handle the technical input/output aspects easily and would prefer to leave that to others. But I am able to recall the circumstances of those early days and feel it is important to get them right. I shall send you an email shortly with some suggestions for how the History section might be revised. Best, Withead (talk) 14:34, 11 May 2011 (UTC)[reply]

Great, I'll wait for your email. Do be sure to include a return address (currently your settings don't allow for you to receive email through Wikipedia). Note that the more important history section isn't on the HeNe laser page (although that does need work) which is a rather short article. I was more concerned with the Laser#History section which is part of a much longer article and which is already a fairly long and detailed section. It mentions just about every notable first in the early development of lasers with the exception of the first visible CW laser or the first visible gas laser! (Or for that matter, the overwhelmingly most common laser for the first 25 years after the laser's invention.). So that clearly needs augmenting and I'd appreciate any material (or citations to material) you could make available. -- Interferometrist (talk) 17:26, 11 May 2011 (UTC)[reply]

I hadn't seen the long article on laser History until you drew my attention to it. Yes, it could use some work. Here is how I would revise the history section associated with the HeNe laser.

History of HeNe laser Development The first gas laser, invented at Bell Labs in 1960 (1) shortly after laser pioneer Theodore Maiman (2) demonstrated the ruby laser, used an electrical discharge in a helium-neon gas mixture to generate continuous infrared radiation at 1.15 microns. Some months later in 1962, it was discovered by other scientists at Bell Labs that essentially the same helium-neon discharge was also producing population inversion in a different group of neon levels which led to the generation of coherent visible light at 0.633 microns (3) As mirror coating technology improved, visible laser oscillation was realized at other lower gain transitions in the same group of neon energy levels.(4) Over the years it has become clear that the He-Ne discharge is a prolific gain medium. Neon laser transitions in this discharge number over 200 and occur at wavelengths from 124 microns in the infrared to 0.540 microns in the visible. (5) If the discharge is pulsed at high current, several transitions in the neon ion become inverted and oscillate. An extremely high gain (>30 db/meter) transition at 3.39 microns originates from the same upper level as the 0.633 transition. If this high gain transition is insufficiently suppressed, it will deplete the upper level of the 0.633 transition and inhibit oscillation at that wavelength. The most widely used gas laser at the present time is the HeNe laser operating in the red at 0.633 microns.

<references> (1) Javan, A., Bennett, W. R., Herriott, D. R. Phys. Rev. Lett. vol 63, pgs. 106 - 110, 1961 (2) MaiMan, T. H. Nature, vol 187, pg. 493, 1960 (3) White, A. D., Rigden, J. D. Proc.IRE, vol 50, pg. 1697, July 1962 (4) Willett, C. S. "An Introduction to Gas Lasers" Pergamon Press 1974, pgs. 407-411 (5) Beck, R., Englisch, W., Gurs, K. "Table of Spectral Lines in Gases and Vapors" Springer Verlag, Berlin, 1980

Other useful sources: Most accurate for people and dates is probably Joan Bromberg's "The Laser in America 1950 -1970 MIT Press 1991. Bromberg conducts personal interviews with most of the laser pioneers. Jeff Hecht's books are usually quite accurate. The Handbook of Laser Technology 3 volumes, edited by Colin Webb and Julian Jones. IOP Publishing 2004 Excellent and comprehensive treatment of all aspects of laser technology by experts in the field. Both Garrett and Bloom have published good books on Gas Lasers. W. R. Bennett has an excellent review article on Gaseous Optical Masers in Applied Optics Supplement on Optical Masers 1962. It covers virtually all the work on gas lasers done up to the end of 1962. Note the author avoids using the term "laser" Bennett also writes about the first gas laser in an article in the millenium issue of Journal of Quantum Electronics, pg 869-875 vol 6 No. 6 Nov/Dec 2000 titled "Background of an Inversion, The First Gas Laser" Well worth reading for background story of 1.15 micron laser. My email address is: adwhite99@comcast.net MZMcBride (talk) 22:19, 19 May 2020 (UTC)[reply]