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

[Dave]

> Message: 4
> Date: Thu, 18 Nov 2010 22:50:34 -0500
> From: "laser"<laser at codeadam.com>
> Subject: [Laser] Some History of the ~100 year old LED !!
> To: "Free Space LASER Communications"<laser at mailman.qth.net>
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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
>
> =====
> "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."
> =====
>
> 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!

Don't forget that H. J. Round discovered the LED effect in Carborundum in
about 1906 (published in "Electrical World" in the 9 February 1907 edition):

http://en.wikipedia.org/wiki/H._J._Round

So, that makes LEDs well over 100 years old.

Dave
WA4QAL