A while back I invented this carbon nanotube amplifier scheme that I think is quite practical and valuable. The invention allows the fabrication and practical use of linear conductors as antennas with lengths that correspond to light wavelengths and therefore allows the application of radiowave antenna, transmission and radiation practices, including harmonic generation and mixing, detection and frequency multiplication, to the lightwave regime. It uses the nanotube as part of a mixer in which a second signal is provided or injected, and the sum or product of the two mixed signals represent a gain in signal strength. It can be used over a wide bandwidth, from the visible light into the RF regimes. Armstrong's superheterodyne radio invention from the early part of the 20th Century could never have anticipated this, but it does provide the heterodyne principle, which is a crucial part of virtually all wireless communications, radios, cell phones and many other important electronic and photonic devices.
Here is a link to a patent that covers the carbon nanotube amplifier invention.
Because it is the first of its kind, I was awarded broad claims. Here is one
A method of amplifying a signal with a carbon nanotube device, comprising: applying a first signal to said carbon nanotube device; applying a second signal to said carbon nanotube device; and outputting a sum or product of said first signal and said second signal from said carbon nanotube device.