Re: how the laser happened

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