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From: Jeff Liebermann <jeffl@cruzio.com>
Newsgroups: sci.electronics.design
Subject: Re: how the laser happened
Date: Tue, 25 Jun 2024 11:40:43 -0700
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On Tue, 25 Jun 2024 08:19:03 -0700, john larkin <jl@650pot.com> 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:
<https://www.google.com/search?q=%22The+Scientific+American+Book+of+Projects+for+the+Amateur+Scientist%22&tbm=isch>
I built something called "A Homemade Atom Smasher", which smashed
everything nearby except atoms.  My father confiscated the book but
later relented.
<https://geoffcain.com/blog/diy-60s-fun-from-the-amateur-scientist/>

>>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:
<http://www.learnbydestroying.com/jeffl/crud/Premature-Judgement.txt>
Yet another list of predictions and premature judgments:
<https://www.reddit.com/r/pbsspacetime/comments/jpfik5/my_collection_of_quotes_of_wrong_predictions/>


-- 
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558