Path: ...!eternal-september.org!feeder3.eternal-september.org!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Jeff Liebermann Newsgroups: sci.electronics.design Subject: Re: how the laser happened Date: Tue, 25 Jun 2024 11:40:43 -0700 Lines: 96 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: individual.net oI4mA6Yt0MBmDf6JDSymNAFx8tx+bkPs4ke7mDFj9mHkVOKGlD Cancel-Lock: sha1:ZsITW62yGpQ5O6sIelnLA92lTW0= sha256:B7c3oqpd0xhq33SwHuIuAVvrmNkk3/fhNDs6ETXmKaI= User-Agent: ForteAgent/8.00.32.1272 Bytes: 5284 On Tue, 25 Jun 2024 08:19:03 -0700, john larkin wrote: >On Tue, 25 Jun 2024 11:50:05 +0100, Martin Brown ><'''newspam'''@nonad.co.uk> wrote: > >>On 21/06/2024 14:05, john larkin wrote: >>> There was a thread somewhere above about photon wave/particle duality. >>> >>> >>> This is worth reading: >>> >>> https://www.amazon.com/How-Laser-Happened-Adventures-Scientist/dp/0195153766 >>> >>> Einstein, in one of his fits of genius, predicted in around 1916 that >>> under the right conditions, a photon could pass by an excited atom and >>> the atom would kick in another photon, or add to the wave amplitude, >>> depending on how you feel about these things. He called it stimulated >>> emission. He also declared that the laws of thermodynamics made this >>> effect impossible to use in practical situations. >>> >>> In 1951, Charles Townes invented a work-around trick and built the >>> maser, a gaseous microwave oscillator. His superiors thought he was >>> crazy to dispute Einstein and almost threw him out of grad school, but >>> it worked. >> >>More interesting still nature beat him to it. >> >>The natural source W3(OH) dense molecular cloud which has hydroxyl >>masers pumped by UV bright young stars embedded in it. >> >>Very bright ultra narrow band point sources on a fuzzy nebulous object. >> >>https://articles.adsabs.harvard.edu/pdf/1981MNRAS.194P..25S >> >>> What's interesting is that any decent neon sign shop could have built >>> a HeNe laser in 1920. >> >>They would have needed to make the mirror just cavity right though. > >I know a guy who built a HeNe. It wasn't hard. I helped do that at a former employer in about 1972. Sorry, no photos. The laser was used to trim resistors on ceramic hybrid twin-T CTCSS (continuous tone controlled sub-audible squelch) for the 2-way radio business. Sorry, no easy to find photos, but I do have some sample hybrids buried somewhere. As I recall, we initially did everything wrong. But eventually, all the parts, pieces and processes were convinced to function properly. My favorite "oops" was when someone decided to mount the laser tube on a brick wall. That actually worked well until someone mentioned that there were train tracks on the other side of the brick wall. I have some hybrids where the laser trim line resembled a seismograph plot. In retrospect, it really wasn't that difficult to build if we had followed the instructions. Just one problem... there were no instructions in 1972. >>A nitrogen gas UV pulsed laser is possible just by getting the pressure >>right and creating the population inversion. Self starting - there was >>a (dangerous) experiment in SciAm Amateur Scientist column to do it >>sometime in the 1970's. June 1974 in fact - cover shows the BZ reaction. >> >>https://www.scientificamerican.com/article/the-amateur-scientist-1974-06/ I have the book "The Scientific American Book of Projects for the Amateur Scientist" circa 1960. There are more recent versions available: I built something called "A Homemade Atom Smasher", which smashed everything nearby except atoms. My father confiscated the book but later relented. >>The failure to discover fullerenes in soot was a lot more surprising >>since they were there all the time since the invention of fire just >>waiting to be extracted by benzene. For a long time space dust had a >>spectrum that could not be reproduced on Earth by any known compound. >> >>Much like Helium was in the sun but more pervasive. > >Too many powerful old farts declare things to be impossible. Here's a list of some powerful old farts and their pontifications. The list has been useful in the presence of experts, consultants and non-technical managers. I don't recall from where I stole it: Yet another list of predictions and premature judgments: -- Jeff Liebermann jeffl@cruzio.com PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558