Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: how the laser happened
Date: Thu, 27 Jun 2024 02:49:37 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 100
Message-ID: <v5ik01$2i4kk$1@dont-email.me>
References: <s2ta7jpomhs58bnntb4nut6pqc4ljskpac@4ax.com>
 <v5e7cv$1gvd9$1@dont-email.me>
 <jonl7jd22ddhsmdpf7g82heo324ebi81p8@4ax.com>
 <jaem7jdg7ke91va9vfoffh232ne8j7g3ui@4ax.com>
 <3ihm7j9kruqmsg57svadl10araoahldqrn@4ax.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Injection-Date: Thu, 27 Jun 2024 04:49:38 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="7fc924c350f1e0ccc961e321b1e2f196";
	logging-data="2691732"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19PtrGbaR+g5mZqLN7BNqMd"
User-Agent: NewsTap/5.5 (iPhone/iPod Touch)
Cancel-Lock: sha1:E8hrdruUS/rFb8DeAHGnijK6AUw=
	sha1:1N1Osu7a9z/0EhFS6Ll+yIv3cKg=
Bytes: 5211

john larkin <jl@650pot.com> wrote:
> On Tue, 25 Jun 2024 17:43:56 -0400, Joe Gwinn <joegwinn@comcast.net>
> wrote:
> 
>> 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.
>>> 
>>>> 
>>>> 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/
>>>> 
>>>> 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.
>> 
>> .<https://en.wikipedia.org/wiki/Planck%27s_principle>
>> 
>> This is often paraphrased as "Science progresses one funeral at a
>> time".
>> 
>> Joe Gwinn
> 
> I see the same thing in electronic design. People favor accepted
> practice, validated in textbooks, and apply all their intelligence to
> showing how new ideas won't work.
> 
> A recent case is deciding that the LC's at the output of a switching
> power supply are "a filter" so must follow  classical filter theory,
> pole-zeros and Butterworths and such. I tell them "It's just a power
> supply."

Classical filter theory is very useful for designing a power supply , as
long as you don’t just wave some canned design over it like a dead chicken.


Controlling rolloff and ringing over a wide range of conditions is easier
with a bit of theory—you can estimate the overshoot via the Q of the
network, for instance. 

Canned designs such as Butterworth, Chebyshev, and so on assume constant,
resistive source and load. While that’s a useful fiction in lots of
signal-level applications, it’s not remotely true in a power supply. 

Cheers 

Phil Hobbs 



-- 
Dr Philip C D Hobbs  Principal Consultant  
ElectroOptical Innovations LLC / Hobbs ElectroOptics  Optics,
Electro-optics, Photonics, Analog Electronics