Phil Hobbs said:
What I was hoping to do was to rent all the old varactor parametric
devices, such as frequency dividers and paramps, and do the same thing
in the infrared. So yes, if you can actually make tunnel junctions
with negative barrier heights that are chemically stable, it ought to be
possible to make circuit-style frequency dividers.
(I may revisit this if I get any customer interest--I was doing a
seedling with a big defence company a couple of years ago, but the
follow-on DARPA program never got funded. I think you can do a lot of
cool stuff that way.)
That would be very neat. I could imagine, say, for the utmost accuracy,
start with a Rb or Cs microwave source, amplify if necessary, then start
multiplying harmonics out. By the time you get to infrared, you've got
zillions of channels, phase locked to a highly stable and pure reference
(depending on how much phase noise adds up in the process, hmm), and the
same thing on the receiver side can demodulate each band down in parallel
for slower processing (i.e., gigabits/ch into an FPGA). Downsides
include, once you get to the 20th harmonic from multipliers and you've no
power left, how do you amplify the THz without another amp (as such)? But
then, that's what the parametric mumbo jumbo is for.
How wide is the average IR "channel"? Say, a few percent out of 300THz is
a *lot* of bandwidth. And the coherent wideband (or comb spectrum) could
do very interesting optical interferometry, especially with a phase
sensitive detector -- correct me if I'm wrong, but that's kind of a holy
grail among optics, right?
Tim
