Terahertz antennas are the hot new research topic. I’m afraid you won’t find many books on the matter just yet. Few articles on the web are written on the topic though from time to time
https://www.technologyreview.com/2013/03/05/179586/graphene-antennas-would-enable-terabit-wireless-downloads/
As a rule, the greater the frequency the smaller the wavelength. Smaller the wavelength, the smaller the antenna. Terahertz frequencies are so high that the antennas are nano scale. So while you won’t be able to find much on antennas in particular, nano tech is a well researched topic with plenty of material available.
For example here is the page on wikipedia that details 7nm chips used in semiconductors.
https://en.wikipedia.org/wiki/7_nanometer
It's the same theory, through and through. Nothing changes. [1]
Now imagine that you succeed in building a terahertz antenna. What is the next step? How much energy can a nano material capture? You will then find out that what you need is an array of nano materials that cover a surface wide enough to capture incident energy (the same way it happens with solar energy). But then the resulting antenna is no longer nano scale. It can be picked up, moved around. Are there materials that interact with terahertz frequency directly?
Certainly. Fiber optics, prisms, lenses. How is their interaction different from the chip level interaction of Radio waves?
Here again you will find very interesting overlaps from motherboards that aim to replace system busses with fiber optic cables
https://spectrum.ieee.org/semiconductors/optoelectronics/get-on-the-optical-bus
To full blown photonic computers.
With that out of the way. Terahertz frequencies are available to us naturally. Visible light, infrared, ultraviolet energy is plentiful in nature. As a result the natural environment is very well adapted to this technology. Research in optics spans centuries and ways have been found to play with light even before its properties were understood. At terahertz scale, you may not even need an “antenna”, the typical conductor or dielectric that produces the wave.
Would you call a Solar panel an antenna?Or perhaps a rectenna? If not, then why? It most certainly produces an electrical signal when an electromagnetic wave strikes its surface?
Would you call an LED a transmitter? If not, then why? It most certainly transforms an input current into an electromagnetic wave that propagates.
Similarly the technology used in remote controls use terahertz InfraRed waves. The circuitry is cheap and widely available.
Traditionally in an electronic circuit the wave is produced with the arrangement of oscillators. Phase lock loops are used to synthesize frequencies
https://en.wikipedia.org/wiki/Phase-locked_loop#Frequency_synthesis
They often combine multiple electronic oscillators
https://en.wikipedia.org/wiki/Electronic_oscillator
[ For example this quora answer describes how to make a 2.4 ghz oscillator https://www.quora.com/How-do-I-make-an-oscillator-that-generates-2-4-ghz-of-frequency/answer/Sumeet-Singh-5?ch=10&share=f199a474&srid=LNunv]
For producing terahertz frequencies special chemicals are used to produce what is known as emission spectrum
https://en.wikipedia.org/wiki/Emission_spectrum
Different colors of light (all in terahertz range 430-770) are produced by selection of different chemicals(phosphors) that emit in that spectrum
https://en.wikipedia.org/wiki/Light-emitting_diode#Colors
The key problem in communication with the emission spectrum is that while we can control electrical signals, chemical processes(phosphorescence/fluorescence) are very hard to control precisely. And as such the resultant wave becomes difficult to modulate. So we are back to square 1.
[On the other hand phosphors are very popular in display systems where the emit light of a particular color that is decoded by our eyes]
It's not at all difficult to produce terahertz frequency. Natural materials do that all the time. But it may not be so easy to modulate it and transmit useful information.
On the flipside, while lenses and reflectors are an interesting research topic at gigahertz frequencies they are normal (boring for researchers) at terahertz. It may be a good idea to study and translate the lessons that you have learned in optics into Radio engineering. And the lessons that you have learnt in radio engineering into optics. Instead of saying that a lens focuses a beam of light you have to start thinking in terms of “Beamforming, waveguiding,sectoring” etc, etc. Just turn around the concepts.
Terahertz is very wide in scope. You need to select the wavelengths you want to focus on and then read up on the materials & tools used to manipulate them.
References
[1] You may want to look into optical rectenna that has been manufactured to turn visible light directly into electricity
https://en.wikipedia.org/wiki/Optical_rectenna
Wikipedia has a page on terahertz radiation and its application with plenty of papers linked in the references section
https://en.wikipedia.org/wiki/Terahertz_radiation
Akshat Jiwan Sharma–Strategy Consultant Mobile/whatsapp:+919654119771 email:getellobed@gmail.com
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