Wonder if the following phenomenon operates in reverse? Does
"self-difference frequency mixing" sound a bit like (sub)super-radiance?
"Terahertz-wave generation in quasi-phase-matched GaAs"
by K. L. Vodopyanov et al. at Stanford
The authors demonstrate an efficient room temperature source of
terahertz radiation using laser pulses as a pump for GaAs structures,
which serve as a nonlinear optical medium. GaAs is also a semiconductor
used in LEDs.
The optical-to-terahertz photon conversion efficiency is only 3.3%. But
that is for coherency and hey, in the reverse direction, the efficiency
may be not terribly important since there is a fair amount of "free"
(ambient) terahertz radiation all around us, no?
In the optical rectification process at Stanford, terahertz output
is produced in an electro-optic medium via self-difference-
frequency mixing between Fourier components of the optical
pulse. Not sure I have a grip on that yet. Lee et al. had demonstrated
something similar in a quasi-phase-matched structures, where the
interaction length between terahertz and optical pulses can be
dramatically extended. That sounds like an analogous situation to the
"extended" near field one sees in RF...
http://www.stanford.edu/group/fejer/fejerpubs/2006/Vodopyanov_APL2006.pdf
Hmm...
Optical radiation <---> Terahertz radiation
Big wl gap there, but ... a most interesting possible, but unproved,
reciprocality.
Jones
