Maybe this yahoo group is more fit than
sci.techniques.spectroscopy for me. I'm writing a
small science fiction novel, and I'd like to design an
intelligent ("sentient") alien with a spectroscopic
sense in their insect-like antennae (the antennae are
short cylinders 5 cm long, 2-3 cm diameter), and maybe
you can suggest me a good design for such
spectroscope.

Using chitin-like materials it's easy to make small
lenses, diffraction gratings (and even rough mirrors,
alternating many thin layers of air and chitin).
Inside the antennae there's small space, and the
weight have to be low (diffraction gratings are
lighter than a solid prism).

I think that such spectroscope can be static or
dynamic. For the static design there can be a whole
line of photoreceptors (tuned to different
frequencies), or even more than one. For the dynamic
design there is a single small round spot of
photoreceptors (tuned for a wide range of frequencies)
and something have to move to show different light
frequencies to the sensor. The dynamic design is
slower, more complex and it requires a neural memory,
but maybe it can be made smaller.

The operation range can be from red to UV (I don't
know if chitin-like materials are transparent in IRs
too).

Some questions:
Which is the best design for such antennae (single
prism, 3 alternated prisms, a diffraction grating,
Echelle, etc)?
How big is it?
How many frequency bands? (25? 200?)
Sensitivity?
Final use: can such spectroscope be used to recognise
materials far away? Other possible uses into a wild
environment or into a "tech" one?

If you are interested, I can write (and ask) something
about how such aliens can communicate such spectra
each other (using voice or other channel).

Thank you,
leonard

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