[Laser] Some History of the ~100 year old LED !!

[laser]

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----- Original Message ----- 
From: "Tim Toast" <toasty256 at yahoo.com>
To: <laser at mailman.qth.net>
Sent: Thursday, November 18, 2010 9:06 PM
Subject: Re: [Laser] led trx

>  I'm still not sure if it isn't
> the first single optic transverter though?? - something to hash
> out maybe!
>
> -toast
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I think that was done in 1980 by Forrest M. Mims III (born 1944).

http://en.wikipedia.org/wiki/Forrest_Mims

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"Using LEDs as narrow band light sensors

Among Forrest Mims many accomplishments, he was the first person to realize
that LEDs (Light Emitting Diodes) had the ability to not only emit light,
but also to sense light. This dual-action (emission/detection) of LED's
or "Mims Effect" was unknown before his discovery.

While studying government (my major) in college, I found that certain 
silicon photodiodes can emit near-infrared radiation that can be detected by 
similar photodiodes. I managed to send modulated tones between such 
photodiodes. In 1971 I demonstrated the ability of many LEDs to detect light 
while experimenting with an optical fiber communication system. By placing a 
single LED at each end of the fiber, it was possible to send signals both 
ways through the fiber with only a single, dual purpose semiconductor device 
at each end of the fiber.

In 1980, Mims demonstrated the dual use concept of LEDs by building a
bi-directional LED voice-communication circuit that allowed two people to
transmit speech optically through the air and also through a 100-meter
section of optical fiber. This demonstration was done at 1325 L Street in
Washington D.C. - exactly the same site where Alexander Graham Bell invented
lightwave communications exactly 100 years earlier! Present for the
demonstration, which was sponsored by the National Geographic Society, were
representatives from National Geographic, the Smithsonian Institution and
Bell Labs."
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I think the hardware was featured as a construction project by Mims in
Popular Electronics around the same time.

Something else I learned quite some time ago is that the LED is approx. 100
years old!!!  Yes ONE HUNDRED !!! Most people think LEDs have only been
around since the 60's.

http://en.wikipedia.org/wiki/Oleg_Losev
and
http://www.orc.soton.ac.uk/fileadmin/downloads/100_years_of_optoelectronics__2_.pdf

If for some reason the links don't work to a search for:

> Oleg Vladimirovich carborundum crystal LED

I remember stumbling across this effect many years ago (not quite a 100 but
it seems like it :-^) when I was playing around with crystal sets and cat
whisker detectors using various mineral rocks as detectors.  Of course my
favorite was galena, (iron pyrite) also known as fool's gold.  Although I
managed to improve the sensitivity of the galena detector by applying a
slight bias (I could hear weaker stations) I kind of lost interest in the
effect as my primary goal was trying to improve the volume level, something
which the bias had little or no effect.

The shock came when I swapped the galena crystal for a chunk of carborundum
(silicon carbide).  The carborundum crystal was always noticeably less
sensitive than the galena crystal so I proceeded to use the same bias
technique I was experimenting with on the galena crystal with the hope that
I could make the carborundum crystal at least as sensitive as the galena
crystal.  Although I didn't notice it at first (because it was daylight),
late one night as I was moving the cat whisker around in a dimly lit room
and playing around with the DC bias I thought I saw a very dim light coming
from the point where the cat whisker was touching the caborundum.  Although
it was difficult to re-produce on a regular basis it was always possible to
achieve after some playing around.  And it wasn't the cat whisker or the
rock glowing from heat as the current wasn't high enough to heat either.
This was a cold light!

Back then there was no internet so it wasn't until many years later that I
discovered that the effect was discovered and documented by Oleg
Vladimirovich and published in 1927 in the journal Telegrafiya i Telefoniya
bez Provodov (Wirelsss Telegraphy and Telephony) in Nizhniy Novgorod,
Russia.  He published 16 papers on the effect between 1924 and 1930.  He
even modulated the emitted light at frequencies up to 78.5 Khz by applying
AC current to the contact.

Most remarkable for a technician with no academic qualifications!!!

So when someone brings up the subject of subcarriers and LEDs it's really
not as new as most people think!!!  Nor is using an LED as a detector or
using the same device as both emitter and detector!