[Laser] grating?

[Thomas Upton]

A diffraction grating (according to my very distant Physics class) was
originally a reflective surface with hundreds of parallel grooves cut
into it.  When the light hit the surface, it was broken up into the
spectrum of the incident light.

You may have noticed the similar effect on a CD or DVD, where rainbow
colors are produced that often show the composition of the sun or
florescent light, for example..

The value of the grating, as I perceive it, is that the size of its
surface is larger than most available transmission prisms (that is, the
light passes through them) which would also allow for spreading the
spectrum of the incident light.  And besides, glass does tend to
attenuate certain colors, most noticeably UV.  We say that the UV rays
in a car are attenuated by the Glass of the windows.  In a reflection
grating, however, there is no attenuation..

Now, as I see your proposal, you want both to broadcast and receive in
the UV region.  Let us say that light for us is red through violet, our
visible spectrum.  If the light that arrives contains red, green and
blue (the ingredients of the white Light Emitting Diode for example)
then a sensor active to each of these primary colors can be placed where
that color shows on the portion of the "rainbow" that would be caused by
the grating.  Consequently, as I see it, at least these three separate
signals, each one of the LEDs capable of modulation at 50 MHz or higher,
could be contained in the same bundle of light, and each "decoded"
without the need for a specific filter.

In reverse, the emitting wave from any emitter could be placed at the
same spot on the spectrum (I am talking about your box you receive
signals in), and be expected to be transmitted essentially in the same
direction as one another.  There would be some  finesse in direction
here, of course.

Incidentally, the "Tricorder" of Star Trek fame could be three LED's at
their own points in the spectrum, each transmitting to the object, and
each receiving a calibrated response.  The quality of the three colors
might give some idea of the spectral analysis of the object, that is,
what it is.  Better minds than mine would be needed to do the work.

In your case, if the incoming light is taken at a point of the spectrum
"beyond violet", it is one or another kind of UV.  No filter, no
attenuation.

As there are many on this List much more proficient than I, the question
whether a diffraction grating would accomplish what you were looking for
arose.

Incidentally, be very careful at the UV frequencies.  There is
tremendous power, capable of much damage.  Your eyes and skin could be
irreparably affected.

By the way, I head on a vacation from Sunday 11th to Monday 19th.  I
will look for the discussion on the List.  I leave it to you as to
whether or not you extend this answer to the List.

Best to you,

Tom Upton  AD6N

KD7JYK wrote:

> What is a difraction grating?
>
> Kurt
>
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