Re: pinhole light antenna

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From: Paul Doherty (pauld@exploratorium.edu)
Date: Fri Dec 03 2004 - 14:22:12 PST 

Message-Id: <l0311072fbdd696431cb0@[192.168.112.30]>
Date: Fri, 3 Dec 2004 14:22:12 -0800
From: Paul Doherty <pauld@exploratorium.edu>
Subject: Re: pinhole light antenna

Hi Eric

Of course atoms absorb and emit light, which is also what an antenna does.
Although with the carbon nanotube light antenna what they really want to do
is to detect light.

However the absorption by an antenna is sensitive to the length of the
antenna which is adjustable.

A short antenna (much shorter than a wavelength of light, green is 550 nm)
absorbs very little of the passing light energy, Make the antenna longer
and the absorption increases until the antenna length is 1/2 of the
wavelength (275 nm) then as the antenna gets longer still the absorption
decreases again. So you can make an antenna tuned to specific wavelengths.

There are some regions of the spectrum in which it is extremely difficult
to make a detector, such as in the submillimeter wavelength region. These
antennas will fill a great need in that region. Atoms and molecules already
do a good job in the visible region.

Paul D

>what exactly is a light antenna? didn't edison invent a visible light
>transmitting antenna when he finally made a fillament? or are we talking
>about some kind of coherent, modulated visible light? --eric
>
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